Into the Lost Worlds

 This excerpt is from Into the Lost Worlds, a novel that has already been published in Japanese on Kindle. What you see here is a portion of the book translated into English and shared

Chapter One: The Time Traveler

1

Would you laugh if I told you that a civilization once existed on Mars, and that at exactly that time, a civilization equal to or perhaps even surpassing our current one existed on Earth? 

You'd say it's impossible, wouldn't you? Or would you listen seriously, thinking that such things might not be so strange after all? I suspect most people would fall into the former category. I can't blame them. Until recently, I would have frowned or laughed it off myself if someone had told me such a thing. Impossible, I would have said. Absurd. But the truth is different.

To be honest, I've just returned to the present day from Earth five hundred thousand years in the past. No, I'm getting ahead of myself. Let me back up. I should start with how I came to believe that a civilization once existed on Mars, and why I was able to travel to Earth five hundred thousand years ago. What I'm about to tell you is the absolute truth. I hope you'll believe me.

2

Let me tell this in order, starting from the beginning. Despite what I wrote above, I should admit that I'm actually someone who enjoys occult topics—things like out-of-place artifacts, the continent of Mu, ancient nuclear wars, that sort of dubious stuff. Far-fetched. Outlandish. Super-scientific stories.

 But please don't misunderstand—it's not that I seriously believed in these things. (Though as it turned out, some of them were true.) I just thought it would be interesting, entertaining if such things were real. I enjoyed them as reading material, as fiction, so to speak. And on that particular day, 

I was surfing the internet as usual, looking for new occult information. However, perhaps because I'd been searching for such information day after day, I couldn't find anything particularly noteworthy. Most of it was either articles I'd seen before or articles that took the occult angle way too far. When I glanced at the clock in my room, the hands were already pointing to two in the morning. 

I was genuinely feeling sleepy. I thought I should just go to bed. But the next moment, I spotted something interesting on my computer screen. It was someone's personal blog, and the title read: "I'm a Future Person Who Time-Slipped from the Year 2100."

It was probably just someone's prank, but as someone who loved occult topics, I couldn't help but be intrigued. Though I anticipated I'd probably be disappointed, I clicked on the site.

You probably won't believe me, the blog's author had written, but the truth is, I'm a time traveler from the year 2100. That seemingly ordinary opening somehow seemed to ostentatiously proclaim that he really was a time traveler, which made it seem fishy, but conversely, the very plainness of the writing style made it seem plausible, and I found myself naturally drawn into the text.

Summarizing the content, it went something like this: He, the blog's author, had apparently time-traveled from the year 2100 to observe Earth's past history. That said, the era he'd originally been aiming for wasn't the present Earth (the Earth time we're living in), 

but a much more distant past. Actually, to be precise, he had apparently reached his intended Earth time originally, but due to a colleague's betrayal (this part struck me as particularly fictional and suspicious), he'd barely escaped with his life to our present Earth. 

As for why he didn't return to his own future, something about timeline relationships made it difficult to return properly. I didn't really understand this explanation as a layperson, but apparently returning to his original future required some complex procedures. However, he couldn't do that at present and was reluctantly staying in our current Earth.

The number of people viewing this blog didn't seem very large, but on the other hand, everyone seemed reasonably interested, and various people had left comments. Most of them were half-teasing comments, though.

 But there were some people like me who were taking it quite seriously, and the blog's author was answering such inquiries as thoroughly as possible. His purpose for time travel. The method of time travel.

 When was the time machine completed? The answers were oddly logical and coherent for something written half-jokingly, and while making me wonder if such things could really be possible, they had a persuasiveness that made me think, well, maybe it really is true.

So I decided to send him a message too. Do you really exist? If you do, would it be possible to meet in person? I have a friend who's researching time machines, so maybe we could help somehow. 

I included my email address at the end of the message and sent it. If you're interested, please email me directly at this address. Then I shut down my computer without expecting much of a reply. 

But surprisingly, when I opened my computer the next day, there was a message from the blog's author.

And the following is the content of the email from the blog's author.

3

Hey, thanks for the message. I decided to email you right away. As I probably wrote on the blog, my name is Tanaka Yuji. You might think it's a strangely ordinary name for a future person,

 but think about it. The year 2100 isn't that far in the future from the world you're living in. Therefore, names are exactly the same as current Japanese names. Well, of course, some people have elaborate weird names, and international marriages have progressed compared to the past, 

so lately there are more people with somewhat unique names. But that aside, most Japanese people in the year 2100 have names no different from your era. Like Watanabe Satoshi. Or Nakamura Satoru. Perfectly ordinary.

...Sorry. I digressed. Anyway, what I'm trying to say is that I really do exist and it's possible to meet you directly. You're still skeptical—or rather, you mostly don't believe it—but I swear I'm a person who came from the future. I'm definitely not toying with you for fun. Please believe me. I know it's difficult. But I can't put it any other way.

Also, the reason I was interested in you was because you mentioned having a friend who's researching time machines. Is that really true? To be honest, I'm in a bit of a difficult situation. 

As I think I wrote on the blog, my time machine is broken and I can't return. To the future. Or to the past, of course. I can't go anywhere. I thought I could fix it myself, but it's been harder than expected. That's because this worldline has a bigger divergence from my worldline than I thought... 

Well, there's no point writing about that. In other words, what I'm trying to say is that I'd be happy if your friend could help me. I have no way of knowing how far along your friend's research is,

 but I'm hoping that maybe, just maybe, it could work out. Well, at worst, even if it doesn't work out, I think it wouldn't be bad to meet and talk with you guys directly. Then maybe a good idea will unexpectedly come to mind.

Anyway, I'm waiting for your reply.

4

I read the email from the blog's author—that is, the letter from the future person calling himself Tanaka Yuji—two or three times. Hmm, I pondered in front of my computer. Common sense would suggest this was just some idle person writing for fun, but on the other hand, my occult inclinations made me wonder if maybe this really was true. All right, 

I decided. It seems fishy, but let's meet this future person calling himself Tanaka Yuji. At worst, even if it's some kind of prank—and that's the more likely possibility—I don't have that much to lose. Even if it's a prank, I resolved that it would be fine either way. And I immediately started writing an email to Tanaka Yuji.

Thanks for the reply. I'm really surprised because I didn't think I'd get a response. Your story is very interesting and exciting. Could we meet sometime soon? 

Honestly, I don't really understand the progress of my friend's research either. After all, I'm a complete layperson when it comes to things like time machines and science. 

But anyway, I'll try contacting my friend. From the perspective of people from the future, the technology of our era must seem very crude, and I don't know if it'll be useful, but still, it's probably better than nothing. I'd be happy if I could help you. But that aside, my friend is very busy, 

so it might be difficult to meet him right away. So, not exactly for that reason, but would it be difficult for you and me to meet first? I'm thinking we could meet first, just you and me, have a simple preliminary discussion, and then arrange an opportunity to meet my friend. It's not that I'm suspicious, but your story is so far-fetched from a modern person's perspective that we can't help but be cautious. 

Especially my friend tends to be skeptical about such things, so I want to meet you directly first and gain certainty myself—certainty that you really are a future person. I apologize if I've offended you. In any case, I'm waiting for your reply.

I wrote something along those lines and sent the email. After sending it, I called my friend. The friend who was researching time machines at university.

５

"What is it? I'm busy right now."

When I called, Manabu Kondo answered in an irritated voice. Whenever I call him, he's always on edge like this. Unlike me, he's incredibly busy. Manabu Kondo is my childhood friend from elementary school, and he's currently working as a physics research assistant at a certain famous university. 

He's the same age as me—thirty-two. Single. He's tall and has such refined features that he could easily be an actor. That's why he's annoyingly popular, but he doesn't seem all that interested in women—or rather, he's the kind of person who puts research first. Right now, he apparently doesn't have a girlfriend. I say "apparently" because I don't really know for sure. I haven't confirmed it.

 Well, not that it matters. In any case, he works as a lecturer at the university while using his free time to continue his own research. I told Tanaka Yuji that Kondo was researching time machines to get him interested, but truth be told, what Kondo is actually researching is quantum mechanics rather than time machines per se. Does that mean I was telling a big lie? 

Not exactly—time machines and quantum mechanics are very closely related. Or so I'm told. I don't really understand the details myself. I'm a humanities person and I don't grasp the finer points of the theory. But I remember when I talked to Kondo before, 

he said that if you develop quantum mechanics far enough, it might actually be possible to build a time machine. So I don't think it's entirely false to say that my friend is researching time machines. In fact, what Kondo is currently researching is apparently experiments in time travel using particles. 

With something as small as particles, time travel might actually be possible. If this research progresses, we might be able to send information to the past or future.

"I know you're busy. But this might be the discovery of the century. I think you'd probably be really interested in it too, Kondo."

Kondo fell silent for a moment, as if weighing what I'd said.

"What is it?"

After a brief silence, Kondo said in a small voice.

"A time traveler."

I said triumphantly.

"Huh?"

Kondo let out an overtly displeased sound. He probably thought I was messing with him. Can't blame him.

"I'm busy right now. I'm in the middle of research. If you called me just to tell some stupid joke, I'm hanging up."

"No, that's not it."

I could tell Kondo was really about to hang up, so I said hurriedly.

"What's 'not it'?"

Although Kondo didn't hang up, he spoke in a quite irritated tone.

"I know it's only natural for you to think I'm messing with you, but I'm not. There might actually be a real time traveler out there."

I tried to make my voice sound as serious as possible so that Kondo wouldn't hang up on me. Perhaps my efforts paid off, because Kondo stayed silent without hanging up. I continued. 

Yesterday, while browsing the internet looking for interesting articles, I happened to find a blog by a person from the future claiming to be from the year 2100. For a prank, the various explanations were strangely consistent. 

I tried sending an email, and the person actually responded, and we might even meet soon. And various other things about Tanaka Yuji.

"What do you think, Kondo?"

After I finished telling him everything, I asked Kondo.

"What do I think? Well..."

"Do you think it's just a prank?"

I expected Kondo to say in an exasperated voice, "Of course it is." But Kondo's reaction was a little different from what I expected.

"Hard to say. It's probably a prank, but... who knows, maybe it's actually real? The way he describes time travel and everything—those oddly specific details are what bother me."

Kondo spoke in a contemplative tone. I was honestly surprised that Kondo would actually take my story seriously. As I fell silent in my surprise,

"Hey, can you hear me?"

Kondo said loudly, perhaps thinking the cell phone signal had gone bad.

"No, sorry. I can hear you fine. It's just that I never expected you to actually listen to what I was saying, so it feels kind of unexpected."

"You're the one who brought it up."

Kondo laughed lightly at my response, sounding amused. I laughed a little too, as if drawn in.

"In any case, I haven't gotten a reply from this person from the future yet, so I don't know what will happen, but we might meet today or tomorrow."

I said.

"Well, just make sure that person from the future doesn't take you to the future."

Kondo said jokingly.

"Well, that wouldn't be so bad. It might be fun to take a little tour of the future world."

I joked back at Kondo's words.

"Anyway, if he's willing to meet, I'll meet him. It's not every day you get a chance to meet someone from the future."

I continued.

"And depending on how it goes, I might need your advice, Kondo. Like I mentioned earlier, this person from the future is apparently stuck here and can't get back to the future. So depending on the time and circumstances, it might be time for physicist Kondo to step in."

"So it's finally time for this genius to shine, is that it?"

Kondo answered playfully and laughed lightly. I said I'd definitely like to ask for the genius's cooperation and hung up.

６

Sure enough, a message from the person from the future calling himself Tanaka Yuji arrived around evening. Here's the text of that email:

Hey, thanks for replying. Sorry for the late response. I didn't notice I had an email.

I'm not offended at all. Rather, it's unreasonable to expect someone to believe me when I suddenly say I'm a person from the future. It's only natural for you to be cautious. You're probably thinking this guy is crazy, or it's some kind of prank. If I were in your position, I would've thought the same thing. I understand your friend is busy too.

As for your proposal, you're suggesting we meet just the two of us first, right? That's totally fine with me. We could even meet right now if you want. What do you say?

I was honestly a bit flustered when I read Tanaka Yuji's email. That's because I never expected him to so readily agree to meet me. While hoping that maybe he really was a person from the future, in reality I'd been predicting that this was all a prank and that Tanaka Yuji would make up various excuses to keep refusing to meet me in person. 

But my prediction was way off. Tanaka Yuji said he was fine meeting me directly. And since he said we could even meet right now, it threw me off a bit. Hey now, could Tanaka Yuji really be from the future? Is such a thing even possible? 

Isn't that the kind of thing that only happens in movies or TV specials? I felt my palms getting damp with excitement and nervousness. I read through Tanaka Yuji's email again. Then I sent a reply.

Thanks for replying. So, let's get right to it—want to meet today? Anywhere is fine. I'll come meet you. Honestly, I'm pretty nervous knowing I'm about to meet someone from the future.

A reply came back immediately to the email I sent.

Today it is. Got it. How about we meet in front of the Alta building in Shinjuku two hours from now? So you can recognize me easily, I'll wear a red cap. And I'll be carrying a black bag. If you see someone dressed like that in front of Alta, that'll be me. Or is Shinjuku too far from your house? If so, I can adjust to you.

By the way, you wrote that you're very nervous about meeting someone from the future, but please be at ease. Even though I'm from the future, I'm only from about eighty years ahead of your time. I'm a perfectly ordinary person, no different from you. I'm just warning you in advance so you won't be disappointed when you meet me (lol).

As for the meeting place, since there's travel time involved, I'd appreciate it if you could reply as soon as possible. See you then.

I immediately replied to Tanaka Yuji's email.

Thanks for the quick response. Okay. In front of Alta in Shinjuku. That's really close to my house. No problem. So you can recognize me easily, I'll wear a blue cap too. Come to think of it, two guys in red and blue caps. We'll look like a comedy duo (lol).

By the way, you wrote that I shouldn't expect too much from you, but I can't help but have expectations. After all, I'm meeting a real time traveler for the first time in my life.

In any case, I can't wait to meet you in person. See you at 8 PM in front of Alta in Shinjuku.

７

As soon as I finished replying to the email, I shut down my computer and went to the bathroom to shave and brush my teeth, then changed my clothes. 

Of course, I didn't forget to put on the blue cap. All of this took nearly thirty minutes. When I glanced at the clock in my room, it was already approaching seven o'clock. My nearest station is Higashi-Fushimi on the Seibu Shinjuku Line, and from there it takes about twenty minutes to get to Shinjuku by train alone. 

But in reality, I had to factor in the time to walk to the station, wait for the train, and then get to the meeting spot, which made me a little anxious. I usually walk to the station, but this time I decided to take my bicycle. I left the bike near the supermarket in front of the station and dashed to the platform. 

Normally there's a guy monitoring illegally parked bicycles who would stop me, but at this hour he must have been off duty because no one bothered me. When I got down to the platform, a semi-express train arrived at just the right moment. I literally jumped onto the train as it arrived. I was breathing heavily from rushing so much. 

As I stood there panting on the train, I could feel several passengers glancing at me with curious expressions. I couldn't blame them. If I were in their position, I would have wondered what was going on too. Feeling embarrassed and uncomfortable, I walked through the train with my head down and moved to the next car. 

Then I sat down in an available seat. There seemed to be few people heading toward Shinjuku at this hour, and the train was nearly empty. No one was sitting in the seat across from me, and I could see my face faintly reflected in the train window. 

What would Yuji Tanaka, the time traveler, think when he saw me? 

Would he be disappointed that such an unremarkable, dull man had shown up? I examined my face reflected in the window glass. Okay. He'd probably be disappointed, I thought. After all, unlike my friend Kondo, I wasn't particularly handsome. 

Not ugly exactly, but nothing to brag about either. People say it's what's inside that counts, not appearances, but honestly I wasn't very confident about my insides either. I'm lazy, a homebody, not the type to take initiative.

 Well, I don't think I'm a bad person, at least. But when I tried to think of my good points, nothing came to mind immediately, which made me feel somewhat melancholy. While I was mulling over such thoughts, the train arrived at Shinjuku Station. 

I got off and walked quickly through the ticket gate. Being Shinjuku, it was quite crowded, and I couldn't walk as fast as I wanted. Still, I hurried as much as possible and managed to arrive at the destination more than five minutes before the meeting time.

８

I waited nervously for more than ten minutes. I looked around, but there was no sign of anyone wearing a red cap—that is, someone who appeared to be Yuji Tanaka. So it was a prank after all, I thought, feeling both disappointed and, at the same time, a little relieved. 

The truth was, I'd been worried about what I'd do if a real time traveler showed up. As Kondo had suggested, I was slightly afraid that I might be taken away to the future, even though I knew such a thing was impossible.

 Even aside from that, meeting a complete stranger you don't know at all is nerve-wracking enough. Just as I was beginning to relax, "Excuse me," I suddenly heard a woman's voice. Startled, I looked around and saw a relatively petite woman standing right in front of me. 

And this woman was wearing a red cap. Huh? Was this woman standing in front of me Yuji Tanaka? But she was a woman... As I stood there in confused silence, "Are you perhaps Mr. Harada? Mr. Shingo Harada?" the woman in the red cap asked my name while looking at my face with an anxious expression.

"Um, well, yes, that's me," I answered the woman's question somewhat flustered. How uncool of me. But if she knew my name, did that mean she was Yuji Tanaka, the person I'd been exchanging emails with? But she was a woman. Were there women named Yuji? Or had Yuji Tanaka suddenly become unavailable and she'd come as his substitute? 

As I stood there bewildered, "I'm sorry for surprising you," she said, bowing her head. Then she removed the cap she'd been wearing. Her face, which hadn't been clear before, was now revealed in the bright lights of Shinjuku. 

What appeared in the bright light was unmistakably a young woman's face. She looked about twenty-five years old. Maybe even younger. 

She had large eyes, and her nose pointed slightly upward as if in defiance of something. Her small lips, slightly full, were a healthy, bright apple color. Her hair fell to about shoulder length and was dyed a light brown. She's quite cute, I thought. No, not just quite. She was probably the cutest or second-cutest girl I'd ever met in my life.

 There was a possibility she might be transgender, but that seemed unlikely. After all, her voice was completely feminine. Though perhaps nowadays even voices could be feminized. In any case, I immediately took a liking to the woman in front of me. Embarrassingly, 

I suddenly didn't care whether she was a time traveler or not, and I'd become just another stupid guy who's weak for any cute girl. My mind went blank for a moment.

"Actually, I'm Yuji Tanaka. The one who wrote about being a time traveler," the woman who introduced herself as Yuji Tanaka said in an apologetic voice, looking somewhat downward. 

"Excuse me?" I was so dazed that I couldn't quite understand what she'd said. Then she looked up at my face and said, 

"I mean, I'm the person you were exchanging emails with," raising her voice a little. "So, are you saying you're male?"

 I asked what was probably a completely off-base question. She shook her head vigorously from side to side, indicating no. Then, according to what she explained to me, it went something like this: Yuji Tanaka was her older brother's name, and she'd been using a pseudonym on the internet.

 As for why she'd been doing that, half of it was to protect herself from men who would approach her with the goal of meeting women, and the other half was from a playful desire to be someone different from her usual self. By the way, her real name was apparently Yui Tanaka. At least the transgender possibility was eliminated.

"Um. So does that mean the other thing was a lie too? About you coming from the future?" I asked in a slightly quieter voice, conscious of the reactions of people around us. Yui Tanaka shook her head. 

"What I wrote online is true," Yui Tanaka answered briefly. "That I came from the future, and that I time-traveled to the past and ended up in this world after various events.

" I couldn't quite react properly to Yui Tanaka's words. When words like "time travel" and "time travel" came so casually from an actual person, they had an indescribable impact. It didn't seem at all like Yui Tanaka was trying to make fun of me by saying random things. 

However, even if Yui Tanaka was serious, time travel was still so far-fetched that it might make more sense to think she was caught up in some imaginary fantasy. 

But the light in her eyes seemed perfectly sane, and she didn't appear to be possessed by strange delusions. Though admittedly, I couldn't deny there was an element in me that wanted to believe she was a real time traveler.

"Anyway, standing here talking isn't ideal, so shall we find a coffee shop or something?" I said. After speaking, I tried to put on as gentle a smile as possible to reassure her (though from someone else's perspective it might have looked quite creepy). "That sounds good," she said, and for the first time a small smile of relief appeared on her lips, as if she'd finally relaxed a bit.

９

Yui Tanaka and I walked a little through the streets of Shinjuku and found a coffee shop where we could talk comfortably. When the waiter came to take our order, both Yui Tanaka and I ordered coffee.

 The coffee we ordered was brought out right away. I took a sip of my black coffee straight, while Yui Tanaka added plenty of sugar and milk before bringing the coffee to her lips. 

When I felt something constricting around my head, I belatedly realized I was still wearing the blue cap. I pulled it off almost violently. I'm not usually the type to wear caps.

 "That cap," Yui Tanaka, who had been silent until then, said in a hesitant voice. I turned my gaze to her face sitting across from me. "It's more white than blue, isn't it?" I looked at the cap I'd just removed at her observation. Indeed, as she pointed out, the cap I'd been wearing was only blue at the brim; the rest could be called white. 

"That's why I hesitated, you know. Whether you were Mr. Harada or not. But you were the only one wearing a white cap looking around for someone, and well, if you just looked at the brim you could sort of say it was blue. So I took the plunge and spoke to you,

" she said with an amused smile. I smiled wryly and scratched my head. "No, I don't usually wear caps much. I just assumed this was a blue cap." "Technically speaking, it's not," she said with a giggle. I looked down at my cap once more and said, "Well, I guess you're right," admitting it with a smile.

"By the way, I know I'm being persistent, but are you really a time traveler? Someone who came from the future?" I asked again after taking a sip of coffee. Fortunately, the shop was noisy with other customers' voices and music, so my mention of "time traveler" didn't attract any attention. Yui Tanaka nodded her chin up and down in response to my question. 

"Well, I know it's unreasonable to ask you to believe something like this," Yui Tanaka said with a slight grimace, looking at my face. Then, as if remembering, she took a sip of coffee. "But I'm having trouble believing it. That time travel like that would be possible in just about eighty years from now.

" I expressed my frank thoughts. "Certainly, this world line seems to be behind in technological progress compared to the world line I was in..." Yui Tanaka said in a small, thoughtful voice, looking down into her coffee cup. There were various interesting terms in the line she'd just spoken, but I remained silent for the moment, waiting for her to continue.

"But suppose, hypothetically, that a time machine already existed in this world right now. Do you think the person who invented it would announce it publicly? That they'd invented a time machine?"

 "Hmm. I wonder," I crossed my arms and tilted my head at Yui Tanaka's question. "It would be a discovery of the century, so I think if you were a scientist you'd probably want to announce it to the world, wouldn't you?" 

Yui Tanaka shook her head lightly as if what I'd said was nonsense. 

"I don't think so. Well, there might be some people like that. But normally, I think they'd hide it. Because if you had a time machine, you could do all sorts of things. For example, you could go to the future to get information about horse races or stocks and make a fortune. In that case,

 it would be more convenient to keep the invention of the time machine as your own secret, wouldn't it?" "Well, I suppose that's true," I agreed tentatively, though I couldn't imagine someone capable of inventing a time machine doing something so base.

"Besides," Yui Tanaka continued after taking another sip of coffee, "time machine research costs enormous amounts of money. It's not something that can be done within the scope of individual research. Naturally, nations and multinational corporations get involved, 

and if a time machine were actually completed, it would immediately become top secret. It would be placed under strict control, and scientists wouldn't be able to freely operate the time machine, let alone announce it to the world. 

Nations and corporations would try to monopolize the fruits of that research for their own benefit. So even if a time machine had already been completed in this world, most people wouldn't know about it. In fact, even in our world, only a handful of people know that time machines have been completed. 

Though in the distant future, there might be worlds where the existence of time machines is open and anyone can freely use that technology. But at least in the world I was in, it wasn't possible."

I couldn't argue with Yui Tanaka's logical explanation. And what I thought was that the out-of-place artifacts found around the world might actually be things left behind by time travelers from the future. 

Like fossils from hundreds of millions of years ago showing a human footprint crushing a trilobite, or full skeletal fossils of modern humans found in strata from millions of years ago when humans supposedly didn't exist. 

If time machines had been completed, everything could be explained, I thought simply. "I see, indeed... or rather, it's really interesting. Listening to you talk, I'm starting to feel like you really might be someone from the future," I said excitedly. Yui Tanaka responded to my statement with an ambiguous smile, as if unsure whether to smile or not. I sipped my nearly finished coffee.

"By the way, can I ask another question?" Yui Tanaka looked directly at my face as if to say "go ahead." "I'm sort of into stories about time machines and such, and I've read through various books," I said, pausing to look at Yui Tanaka's face. And from what I've gathered reading various books, it seems you need to move faster than the speed of light to time travel. 

How does that work? Time travel to the future aside, traveling to the past seems to require exceeding the speed of light, but according to Einstein's theory, you can't exceed the speed of light. So I was wondering how time travel to the past became possible. I can't imagine how a method to move faster than light could be found in just eighty-some years..."

"You don't actually need to exceed the speed of light to time travel to the past," Yui Tanaka answered matter-of-factly. "Or to go to the future, for that matter," she added. I remained silent, waiting for her to continue. My coffee was gone,

 so I drank some water instead. "Of course, as you pointed out, even in our world we still can't create vehicles that move faster than light... at least not that I know of," Yui Tanaka paused. Then after a little while she began speaking again. "But time travel is possible without exceeding the speed of light. I think such theories had already been established in this world too... like methods using wormholes, or superstring theory."

"Come to think of it, I feel like I've seen things like that," I said with a wry smile. I'd been so focused on the impossibility of exceeding the speed of light that I'd completely overlooked the fact that methods of time travel based on theories like those she mentioned had been proposed. 

However, in any case, those theories were just as difficult with current technology as creating vehicles that could exceed the speed of light. They were merely at the level of being somewhat better—possibly not impossible—compared to exceeding the speed of light, which had been scientifically proven impossible. They weren't things that could be realized in eighty years or so.

"The first time machine in the world I was in was completed in the year 2034. The first prototype was built at CERN—the European Organization for Nuclear Research," Yui Tanaka continued. If what she was saying was true, it meant the first time machine would be completed in just over twenty years from now. "You know about CERN, right?" I nodded at Yui Tanaka's question. 

"It's the world's largest particle physics research facility in the suburbs of Geneva, Switzerland, on the French border, right? I've read about it in newspapers. They have a huge circular accelerator underground with a circumference of 27 kilometers...

 I don't know the details, but... I've heard that by using that accelerator to collide protons at tremendous speeds, they might discover new particles that have never been observed before, or they might even be able to create black holes artificially."

"Yes! That's exactly it. Black holes!" Yui Tanaka said in a somewhat excited tone at my statement. I looked at her face, a little startled. "Time travel uses exactly those black holes," Yui Tanaka said with emphasis. "If you artificially create ultra-microscopic black holes and use them, time travel becomes possible.

" Yui Tanaka picked up the water on the table, took a sip, and continued her explanation. "The time machine uses something called a Kerr black hole.

 A Kerr black hole is a bit different from a normal black hole—it's a rotating black hole. By artificially generating a microscopic singularity and injecting electrons toward its surface, 

you can manipulate mass and gravitational fields. By rotating two manipulated microscopic singularities at ultra-high speeds, you can expand the event horizon within the Kerr local field or Tipler gravitational sine wave. 

Then by passing matter through the ring singularity, time travel is complete. Of course, in this process you need to simulate the operation of sending it to a different world line and adapt, rotate, and move the local field."

"???" Frankly, what Yui Tanaka was saying was completely beyond me. "...Sorry. That's a bit too difficult for me," I said with a wry smile. 

"No, I'm sorry. It's hard to understand for people who aren't familiar with this kind of thing," Yui Tanaka also said with a wry smile. "In essence, we use artificially created black holes to time travel." "I see," I nodded with a feeling that was both understanding and not understanding, unsatisfied.

"But this time machine has various problems. After all, since we're not moving faster than the speed of light, we can't go to the past or future of exactly the same world we were in. 

The time machines in our world might be more accurately described as devices that move to different world lines rather than time machines." "Huh," I interjected, thinking the story was getting complicated again. 

"To simplify and make the story easier to understand," Yui Tanaka said, "this is just an image and differs from reality, but to make the explanation easier to understand, it goes like this. Excuse me,

 could you imagine a circle?" I drew a circle in my head as Yui Tanaka asked. "We use a black hole to make a hole in that circle. And we pass through that hole. When we pass through this hole, time travel is complete, but what lies beyond this hole isn't the world we were originally in. It's the past or future of a different world that closely resembles ours."

Yui Tanaka said this, then took out a paper napkin from the table. Then she pulled out a ballpoint pen from her breast pocket—apparently she always carried one—and drew several parallel lines on the napkin. "Like this, there are multiple worlds similar to ours existing in parallel," Yui Tanaka drew arrows between the lines connecting them. 

"When you time travel, like these arrows, you move to a different world that probably exists in infinite parallel universes." "Parallel worlds," I said. "Yes! Parallel worlds!" Yui Tanaka looked at my face and smiled broadly, like praising a quick-learning student. "What was invented in our world is not so much a time machine as a method to move to parallel worlds—different universes."

"I see," I said, then touched my chin with one hand. The idea of parallel worlds is often used in SF novels as a means to resolve time paradoxes, but it was actually true—I felt excited rather than impressed. "So if I time traveled and killed my own parents, I would have killed my parents in a different world, 

so I wouldn't cease to exist. The world branches and continues to exist separately," I said. "Exactly," Yui Tanaka looked at my face and smiled as if to say "well done." "I see... I understand now," I murmured. "That's why you've been saying things like 'the world I was in' and 'world line' all this time." "That's right," Yui Tanaka said, then drank some more water. A waiter came and refilled our water glasses.

"Until about ten years ago," Yui Tanaka continued her explanation, "we could only time travel to the slightly recent past or slightly near future." I looked at Yui Tanaka's face as if to ask why. "If you try to go to the very distant past or future, 

the deviation in world lines becomes too large, and there's a high probability of ending up in a completely outrageous world. A world far too different from the one we know,

" Yui Tanaka continued, then pointed with her index finger at the napkin she'd drawn on earlier. I looked down at the napkin. "Say the past from ten years ago is this line, right?" What Yui Tanaka indicated was the line connected by arrows earlier. It was adjacent to the line representing the world we're in. "But when it becomes 500,000 years or 100 million years, that line ends up being around here,

" Yui Tanaka drew an additional line in a place quite far from the line connected by arrows. "With the technology from about ten years ago, we couldn't safely move to this line. In other words, we had no choice but to time travel prepared for failure, prepared to arrive in some terrifying world." Yui Tanaka paused there. I silently gazed at the line she'd newly added.

"But recently," Yui Tanaka spoke again, "new technology was developed. We became able to determine with considerable accuracy where exactly the past world we want to go to is located. 

And by inputting that data into a computer, we can go to the desired world almost safely. With the establishment of this technology, we became able to time travel to the very distant past—worlds where dinosaurs were actually alive and moving around. 

Though this technology also has its limits, and we can't time travel to absurdly distant pasts... like the moment the universe was born."

"But that's amazing!" I said quite excitedly. How envious that they could see dinosaurs actually alive and moving. "So was your mission to go see dinosaurs? 

Come to think of it, you wrote in your blog that it was to observe Earth's past... does that mean to study dinosaur biology and why dinosaurs went extinct?

" Yui Tanaka shook her head at my question. Her expression looked somehow sad. "Our mission was to investigate Earth 500,000 years ago. The thing is, something amazing was recently discovered.

 That humanity 500,000 years ago had built a fairly advanced civilization. Even in our world, until recently it was thought that humans only developed civilization around 10,000 years ago, but it turned out that wasn't true. How we found this out was triggered by investigations on Mars..."

I couldn't take my eyes off Yui Tanaka's face.

The novel excerpt above is part of Into the Lost Worlds, which has already been published in Japanese on Kindle. This portion was translated using AI. If you would like to read more of the story, please leave a comment below. If there are many requests, I’m considering publishing an English edition on Kindle as well.