I couldn’t wait another moment, so I paid my tab, dashed out of the bar, and immediately got in contact with Kazune. It was past 10 p.m., but luckily, she was still at the lab. Incidentally, both of us were still single at this point. I may not have had any prospects, but she certainly did, yet she chose to prioritize her work over all else. A scientist in her late thirties probably wouldn’t have an easy time finding a husband, so in a sense, perhaps she was even more of a workaholic than me.
In any case, right then, I was grateful for her presence. I grabbed a taxi to the lab, then brought Kazune into a private room.
“What is it? Is something the matter?” she asked, her expression dubious. I decided to cut right to the chase.
“I’ve found it. A method of time travel.”
Her eyes flew open. A little shock was understandable, of course. The thing we’d been chasing blindly for the past ten years was suddenly right in the palm of our hands. But she had known me for years now—well enough to know that when it came to Shiori, I’d never joke around.
“Explain.”
“Sorry—what I mean is that I’ve got a concept, that’s all.” And so, as I detangled my thoughts, I slowly began to explain my theory. “In the Sea of Einzwach, the world bubbles rise to the surface to represent the passage of time. So to go back in time, they just need to sink.”
“According to the model, yes, but we talked about that on day one. Bubbles can’t sink, so the only way to push them down is to exert some manner of force, but doing so risks popping the bubble entirely.”
“You’re wrong, Kazune. Bubbles can sink…under the right conditions.”
“Such as?”
“Viscosity. Ever heard of Guinness? It’s a viscous beer with very small bubbles. As long as the viscosity outweighs the buoyancy of the bubbles, we can create a downdraft with the resulting vortex that will push the bubbles down.”
“Again, we’re talking about a scientific model, right? It’s just a thought experiment. The hard part is actually achieving it in imaginary space.”
“We can. We just need to modify the IP capsule and IP lock.”
The instant I mentioned the very devices that were close at hand, her expression changed from disbelief to contemplation. That was my cue to explain the specifics.
“First, we expand the functions of the IP capsule to apply external pressure to the time travel subject to compress the associated imaginary elements. Next, we expand the functions of the IP lock to secure the newly compressed elements. Then we overwrite the IP in the surrounding imaginary space and create a small vortex to produce a downdraft. The shrunken elements won’t have enough buoyancy to combat the imaginary viscosity, so in theory they should start sinking!”
Slowly, silently, Kazune digested this information.
“In theory…yes, it sounds possible,” she said. “The problem is whether we can actually implement these expansions for the capsule and the lock.”
“That’s what we’ll research next. Now that we’re able to measure imaginary space directly, I’m sure we’ll find a way!”
“Oh, good grief. Another decade’s worth of work ahead of us…” She slumped her shoulders in defeat. Translation? She was on board. “And there are other problems too. Even supposing we do work everything out, how will we use it to save Shiori-san?”
It was a valid question. That was my ultimate goal, after all, and merely establishing a method of time travel wasn’t enough to achieve that. It all came down to how time travel could save Shiori. But, naturally, I already had a rough idea.
“During this process, bubbles that sink don’t float back up, unlike in the beer. They keep sinking backwards in time until the buoyancy and viscosity levels even out with each other. The key here is that we’ll need to have already found the IP of a world where Shiori will live happily ever after. Then we’ll carefully compress the bubble so it’ll sink all the way to that branching point. If it works, the post-branch bubble should stop and fuse with the pre-branch bubble. At this point, the bubble’s IP is overwritten. Then it reverts to its original size and buoyancy, and the fused bubble starts floating back up toward the future again. After that, I carry on with my life in the other world.”
Kazune listened to my plan with her eyes closed. Then, after a long silence, she opened her eyes and glared at me.
“Let me get this straight. You want to send your disembodied imaginary elements to a branching point in the past, fuse with it, and live your life all over again?”
“More or less.”
“And what happens to your body left behind here?”
“We’re subjecting it to the same conditions as imaginary karyomitosis, except the imaginary elements migrate vertically instead of laterally. If the physical matter is the body, then the imaginary matter is the soul. And without a soul, my body will be an empty husk… In short, brain death, I imagine,” I explained matter-of-factly.
At this, Kazune frowned. She didn’t look happy to hear it. “And who’s going to look after you?”
“Don’t know.”
“How will your mother and father feel after you’re gone?”
“Don’t care.”
Her frown deepened. Obviously, I could understand what she was getting at and how she felt; I wasn’t that heartless. But what else could I say? It honestly didn’t matter to me.
“This world did Shiori dirty, so I don’t care what happens to it. I’m taking her soul and leaving for a world where she’ll be happy. Nothing else matters.”
That was all I had left to live for. I had no use for a world where my Shiori would never be happy, so the two of us would leave. Everyone else could go ahead and enjoy the rest of their lives without us. There wasn’t a single shred of hesitation in my mind; I sincerely wanted this, from the very bottom of my heart. And unless Shiori could magically come back to life with her body intact, nothing could change my mind.
Kazune must have sensed this, because she let out a sigh.
“…For the record, this is a time paradox you’re talking about. If you disappear into the past, won’t every single event you caused disappear along with you?”
“The tenets of imaginary science suggest otherwise,” I countered. “Think of it like if I was a pencil: if it breaks after drawing a line, that doesn’t mean the line goes away.”
“One more thing. If you merge with your parallel self in an alternate universe, your imaginary elements will merge right along with you, so I doubt you’ll get to keep your memories or personality. You’ll lose all the knowledge you gained after the branching point, and you’ll have no choice but to trust your other self to do the right thing.”
“Fine by me. To me, the only real Shiori is the one I met in this world, and I’ll never forgive myself for destroying her life. I reject the event that ruined it all, and I reject the world for letting it happen. If our souls can have a second shot somewhere else, that’s all I need.”
“You’re actually insane, you know that?”
“Yeah, probably. If you don’t like it, you’re free to go. I’ll handle it myself.”
I meant it too. This was my personal research, and she had the right to opt out at any time. But her response betrayed my every expectation.
“Oh, I’m not going anywhere,” Kazune said. “God knows how many decades it’ll take without my help.”
Her expression had lost all edge, like a weight had been lifted from her shoulders. It was funny—I was expecting her to lecture me, or insult me, or maybe even punch me.
“Incidentally, there’s one more problem, isn’t there? If you use the IP capsule for time travel, then Shiori-san can’t go with you. She has no physical body, and her imaginary elements are stuck at the intersection. What’s the point of going by yourself?”
“Oh, right, that… No, I think it should be fine. I mean, our imaginary elements are partially fused together, remember? Any change to my IP ought to change hers too, so if I go back in time, I believe she’ll come with me. But of course, I’ll need to test it first.”
“I see. Sounds like a lot of hard work.”
Kazune shook her head in exasperation. She was acting so normal now that it was hard to believe she called me insane a minute ago. At this point I was getting suspicious, so I decided to ask her about it flat-out.
“So…you’re okay with this?”
“It doesn’t matter what I think. Your life, your choices,” she replied.
“Sure, but I’ve dragged you into it for years now.”
“And that’s my life, my choices. Besides…” She gazed wistfully into the distance and smiled. “I wish I knew what it was like to love someone that madly.”
Indeed, she didn’t seem to have anyone special in her life, not as far as I knew.
“By the way, what exactly qualifies as ‘a world where Shiori-san will live happily ever after’? Isn’t happiness subjective?”
“Yeah, of course. I’m not talking about a perfect world or anything. I just know what sort of world she’s generally the happiest in.”
And my life’s purpose was to take her there.
“Oh really? What sort of world is that?”
Fortunately, I had known the answer to that question for decades.
“A world where she and I never meet.”