Inside the Hongseong Palace.
Fou stared at the images playing on the television and fell into thought.
A form of human amusement he had never seen back in Chaldea.
Onscreen, a man was being forced to do an embarrassing dance as a penalty.
"Huff... huff... This is as far as I go. I'm leaving the rest to you..."
"You think I'm going out there in your place? Let's just stop at the bonus we've got."
"Hey!"
It was a program where the prize money kept increasing the longer someone continued dancing.
One of the two male challengers, working as a pair, gave up midway through.
"In your place," Fou thought.
One man should have taken over for the one who had been dancing, but he refused.
As a result, they lost the prize money.
Tengen watched the scene and blinked.
He valued the greater good, but his attachment to human emotion had grown faint, so he felt little in particular.
At most, it was, "Well, they lost the money."
That was all.
Fou, however, took it differently.
The phrase "in your place" struck his mind like a bolt of lightning.
Substitute. Replacement.
He rolled those similar meanings over and over in his head.
And in the end, he arrived at one answer.
"Substitution."
Substitution Magecraft was the art of offering a price in exchange for carrying out various forms of replacement.
Put simply, it was exchange.
It could alter the material composition of something.
Or it could swap the positions of one thing and another.
Fou could move through space, but that was different from crossing parallel worlds outright.
It was still, strictly speaking, Magecraft.
Traveling between parallel worlds as though wielding the Second Magic was difficult, but exchange...
That was something he could attempt within the category of Magecraft that came infinitely close to true Magic.
To do that, he needed two things.
A target to exchange. And eyes capable of observing that target.
Even observing parallel worlds alone was already close to the Second Magic, but observation by itself was only half of it.
Only when observation, interference, and practical application were all possible did it become the Second Magic.
But half of it would be enough.
There was a chance it could be realized.
He had already mastered the sensation of crossing space itself.
With enough trial and error, he felt he could establish a stable passage.
"Did they say I'd need BB?"
That little devil.
She might still exist even in a world where everything had been rendered as though it had never happened, but he had to try.
Their journey had been treated as though it had never existed and erased.
The lives they failed to save remained unsaved to the very end.
Even so, perhaps the story had ended with someone, somewhere, still reaching a happy ending...
Fou did not think so.
A true happy ending.
He believed a gate leading there would appear, without fail.
And that belief proved correct.
After returning to ordinary life, I started dropping by the Hongseong Palace whenever Fou contacted me.
At this rate, it felt like I visited Jujutsu High more than anywhere else in my life, but I didn't mind.
There was nothing bad about seeing a friend often.
"To achieve this, I'll need an enormous amount of Magical Energy. You happen to have exactly that, so I'd like you to provide some. Can you do it?"
"Of course I can."
It really did feel like my Magical Energy was being steadily drained out of me, almost like giving blood...
But even that sensation was faint.
If I had to compare it to something, it was like scooping a single cup of water out of an infinite ocean.
That was what it felt like.
"With this much fuel, trial and error doesn't cost me anything. At this rate, I should get results soon."
"What kind of results?"
"I return to that side, and you obtain the resources you need."
My eyes widened before I even realized it.
The resource I needed most right now was BB.
"You can do that?"
"I don't know. But if I keep observing, the odds shouldn't be zero. Returning to the original world out of countless parallel worlds is tricky, but it isn't impossible."
"Can you use Magic too, by any chance?"
"Not at all. What I'm trying to do is a workaround. It may come infinitely close to Magic, but in the end, it's still within the domain of Magecraft."
Fou lightly tapped the air with one tiny forepaw.
Each touch sent a small ripple spreading through empty space before it vanished.
Depending on how you looked at it, it resembled a radar pulse.
Or the ripples from a stone dropped into a lake.
I didn't really understand it, but I could tell that every single pulse consumed an absurd amount of Magical Energy.
My sharpened sensitivity to Magical Energy made that painfully obvious.
Ripples pierced through space, spread somewhere beyond it, and disappeared.
And Fou watched them.
The more I looked, the more it felt like watching someone sweep the ground with a metal detector, searching for something buried deep below.
Or like sonar probing the dark from a submarine.
"I don't really get it... but we definitely shouldn't interrupt him, right?"
Ibuki-douji sidled up beside me and asked.
She was on duty starting today, so she had followed me all the way down into the Hongseong Palace.
Backup Shuten-douji was waiting by the tunnel entrance.
Apparently holding a one-woman drinking party.
"Yeah. I don't know much because I'm lacking in magical training, but I can tell this is delicate work. Serious work."
"It looks like he's interfering with space itself... Do you think it'll work?"
"It will. There were plenty of impossible things before, and we still pulled them off in the end."
The final chapter of Part 1.
It had been Fou who threw himself away to save Mash, almost like a sacrifice.
After that, his power had naturally accumulated again, and his intelligence and strength had returned...
But that didn't change what he had done.
I trusted Fou's power. And I trusted his age and experience.
By his own account, he'd spent ages beside that insufferable Merlin. He had to have learned a lot.
After tapping at space for a long while, Fou lowered his paw.
Looks like he was done for today.
"That's enough for now. Can you come again tomorrow?"
"Sure. See you tomorrow. If there's anything you want to eat, tell me. I'll bring it."
"Magical Energy alone is enough, but I'd like some sweet snacks."
"Got it. I'll pick something out myself."
I said goodbye to Fou and left the Hongseong Palace.
I didn't forget to greet Tengen from a distance, either.
Compared to when I first came here, everything felt more relaxed now. More casual.
Even that white space had, over the past few days, started to feel like an ordinary room in a house.
Maybe it was because I came so often that it had grown comfortable.
Or maybe Tengen had just gotten too lazy to change it.
Either way, it wasn't a bad change.
"Back already, my lord? Looks like today was another miss."
When I came back up, Shuten-douji rose from where she'd been sitting with a smile.
It wasn't mockery.
"We just have to trust him and wait. More importantly, weren't you bored waiting around?"
"Me? Nah. It didn't take that long, all things considered. I'm fine, so let's go."
I nodded and took Shuten-douji's hand.
On my other side, Ibuki-douji linked arms with me.
We walked out like that and ran into Itadori Yuji.
Thankfully, he looked healthy.
"Huh? Mr. Kadoc?"
"Yuji. You doing well?"
"Yes. Thanks to you."
The moment he saw me, Yuji bowed first.
He spoke casually even to Gojo Satoru and Geto Suguru, but with me he always used polite speech.
He had back then, and he still did now.
Honestly, being treated specially so consistently felt pretty good.
"Things must be noisy because of Sukuna. It's been rough, hasn't it?"
"I'm okay. I don't know what that guy's thinking, but he's been surprisingly quiet. Maybe ever since he saw you, Mr. Kadoc?"
"He's sly. Means he knows his place."
Shuten-douji slipped that in with a smile.
Come to think of it, that sounded plausible.
At first glance it sounded like she was just insulting him, but there was a real point buried in it. Sukuna understood the situation.
He was cunning enough to read the room.
Maybe that was why he was quietly waiting for the death sentence to come down.
Or maybe he was waiting for an opportunity.
Right now, Sukuna was nothing more than a criminal trapped inside Itadori's body.
On his own, he could do nothing.
Just like in Jujutsu Kaisen, he needed an outside variable. Some moment when Itadori was pushed into crisis.
Or something like what happened right before death.
But there was no such variable now.
And everything that might have caused one was already dead.
So all he could do was wait.
Sukuna was a master at passing time while doing absolutely nothing but existing as a soul, so it probably wasn't difficult for him.
"Even when we provoke him, he stays quiet," I thought.
Considering that rotten personality of his, he should have snapped back immediately, but he stayed utterly silent.
As if he hadn't heard a thing.
That alone proved Sukuna knew when to lie low.
Tricking Kurusu Hana so slyly had probably come from the same instinct.
"Oh. What about Megumi?"
"Fushiguro? He went out on a mission with Kurusu. You know how Kurusu is, Mr. Kadoc..."
I did know, so I just nodded in silence.
Unlike the original flow of events, Kurusu Hana had enrolled at Jujutsu High.
That made her a first-year at Tokyo Jujutsu High alongside Fushiguro Megumi.
Pretty, cute, and hopelessly devoted.
In every way, she seemed like ideal bride material for Megumi.
Which was why Zenin Sae had her eye on her.
I'd also heard she had gotten fairly close to Tsumiki.
"Glad to hear they're doing well."
"Right. So, are you heading home now, Mr. Kadoc?"
"Yeah. I only come here when I've got business at the Hongseong Palace. There's no reason to meet Maki or Mai here."
Come to think of it, was it after they'd gone to the Zenin Clan main house?
The way both of them looked at me had grown a little more intense.
It didn't seem unpleasant.
If anything, they looked serious, but pleased, so it didn't seem like anything bad had happened.
To begin with, the current clan head, Zenin Naobito, was already on close terms with me.
And Zenin Naoya supported me too, so there was no way things could turn hostile.
And if they looked at the Servants around me...
Yeah. Terrifying.
"Anyway, I should get going. Stay healthy, Yuji. If anything gives you trouble, tell me."
"Yes, sir!"
I parted ways with Itadori Yuji as he gave me an energetic farewell.
There had been no results today either, but if we kept trying like this, something had to give eventually.
Fou went on tapping endlessly at space.
He was developing the sensation of spatial movement and his magical formulas further, extending them across dimensions.
Development. Application. Experience.
He was using every card he had to peer beyond the dimensional boundary.
Countless dimensions.
To look across infinite parallel worlds was a journey on a colossal scale.
He had to distinguish with certainty between worlds that were similar, yet different.
He had to brush past worlds completely unlike his own and still find the correct answer.
The process could exhaust him.
He might fail before he even truly began.
Even so, Fou had no choice but to begin.
Beginning was the only correct answer.
"Fou. Fofou. Fou."
Muttering to himself, Fou kept striking space.
He kept knocking as though trying to force open a door sealed shut.
If you knocked, it would open.
As if obeying those words, he did nothing but continue knocking, over and over.
Tengen watched him and drank tea.
Days passed. Then months.
After seeing the same thing repeated so many times, even the vibrations in space had become familiar.
"It doesn't seem meaningless... but is it really doing anything?" Tengen thought.
Another world.
Even with proof right in front of him, it still felt like an absurd goal.
To cross from one world to another.
To broaden one's sight until it could perceive worlds themselves.
Tengen's mind had already drifted close to the realm of a plant, yet even that mind found this fascinating.
It was simply that vast in scale.
"Fou!"
Just as Tengen was thinking that today, too, had come to nothing, Fou suddenly threw his chin up and cried out with all his might.
The way he howled was adorable, but there was also a strange dignity to it.
It suited a being that, if fully grown, could become a monstrous Evil of Humanity.
"Did something happen?"
Tengen found himself focusing on Fou without meaning to.
He wanted to see what the creature would do next.
"Got you."
Fou slowly closed his mouth and lowered his head.
At last, he had found it.
Chaldea, where they had once been.
The atmosphere and texture of the world they had lived in.
There were too many worlds with the same overall structure but different details, enough to make him dizzy...
But by tracing each irregularity one by one, he had finally identified the right one.
Among them, the flow that had once connected to this world.
The lingering trace of that connection had been a tremendous help.
Tengen watched him, then asked carefully, "Have you grasped something?"
"I have. Now I just need to make contact and lock onto it. The situation's different from what I expected, so it's a little strange... but that kind of thing happened all the time anyway."
The moment Fou identified the world he had come from, he could not hide his shock at what he saw there.
Olga Marie, whom he had thought lost in the gap between spaces, was alive.
And Chaldea, which should have vanished, still existed intact.
"What in the world is this?"
That question naturally came to mind, but if anything, it was a favorable development.
It meant the environment existed to call forth the Servant Kadoc wanted with relative ease.
"Sorry, but could you write a letter for me? My hands are like this, after all."
Fou asked that while lifting one tiny, adorable forepaw.
For Tengen, it was no difficult task.
"Very well. Would it be acceptable if I wrote it in Japanese?"
"Yeah. That'd actually be better."
The humans of Chaldea knew many languages.
And the one at the center of Chaldea, the one who had restored Human Order, was Japanese.
In other words, there was no problem at all with writing it in Japanese.
If anything, it made things easier.