Luxury cruise ship, top deck.
Inside the now masterless luxury cruise liner, Rozen and Yukina appeared.
Rozen silently walked forward, with Yukina following closely behind him the entire time.
Together, the two of them passed through a long corridor and entered a VIP suite.
Inside, there was someone.
"...So you've come?"
That person sat at a desk, a laptop in front of them, with a resigned expression that spoke of having given up.
Seeing them, Yukina looked conflicted, while Rozen remained surprisingly calm.
Seeing this, the person instead spoke up.
"You don't seem the least bit surprised that I'm here."
They said mockingly.
But Rozen remained calm.
There was no helping it.
"I already found out while searching for Itogami Meiga," Rozen said flatly. "Though at one point, I thought I had it wrong and even wondered whether Vatler or Itogami Meiga might have taken you hostage to threaten me. But once the power of the 'Cleansing' appeared, I knew—it wasn't strange for you to be here at all."
Why?
"Because without you, neither Vatler nor Itogami Meiga would be able to use the power of 'Cleansing,' right?"
Rozen stated plainly.
That was a fact.
As a highly accomplished mage, Rozen understood well—activating 'Cleansing,' an ultimate forbidden spell, was not something so easily done.
That was a mystery that had stepped into the realm of true magic, a force capable of altering the very world itself. Unless you were a divine being like Cain, how could you possibly wield it so freely?
Even if Itogami Senra prepared Itogami Island as an altar and tapped into the mana of the ley lines to initiate the forbidden spell, that alone wouldn't be enough.
"Even if you've already got the magic circle set up and the mana prepared to be consumed, in order for the spell to be executed, someone still needs to perform the actual operation."
For example, chanting the incantation.
Or forming specific hand seals.
Or perhaps engraving appropriate magic sigils.
All of these are necessary conditions to activate a spell.
Even the miracle of "Heroic Spirit Summoning" in the Holy Grail War or Chaldea's Fate system, despite having all preparations in place, still required the actual chanting of the spell by a qualified Master for the summoning to occur.
If such systems needed that much, then a world-altering ultimate forbidden spell would need someone to personally activate those ridiculously complex arrays.
However...
"Vatler mentioned that 'Cleansing' was reconstructed as a digital program," Rozen continued.
"Just like how Tartarus Lapse's 'Rose' was injected as a virus into the computer world to execute a spell inside the digital realm, if 'Cleansing' was reconstructed in that same format, then it could be computed using the five supercomputers in 'C' and triggered by a highly-skilled hacker. That would work."
That was the real condition for activating 'Cleansing.'
Accordingly, the one capable of launching 'Cleansing' wasn't Itogami Meiga.
It wasn't even Vatler.
It was a skilled hacker.
This hacker was the only one in Itogami Island capable of entering the zeroth layer of the Keystone Gate, logging into the five supercomputers within 'C', using them to run the magical computation, and granting that power to Vatler and Itogami Meiga.
There was only one person on all of Itogami Island who could do that.
"And that's you, Asagi."
Rozen named the person's identity.
The one here was Aiba Asagi.
No, not just Asagi.
"Do I have to invite you out too, Motoki?"
Rozen turned to look at the adjacent partition.
There, a flippant youth wearing headphones stepped out with a headache-like expression.
"Ah, so you figured it out after all."
Motoki scratched his head.
Rozen looked at Asagi, then at Motoki—these friends from the past—and sighed silently.
"I never expected it to be you two... but thinking about it, I guess it's not that strange."
People who had stayed by his, Kojou's, and the others' sides—those with unusual origins—were never going to be ordinary.
If they were just normal people, the Management Cooperative would have intervened long ago.
Even Natsuki had once said that there would be a Lion King Agency observer around him, and Kojou also had someone monitoring him.
And Senga Takehito had clearly stated that the legitimate descendants of the God of Sin—the Forbidden Four—held important posts within Itogami Island.
Didn't all those conditions point perfectly to these two?
After all, Asagi's father was a councilman of Itogami City, with the authority to appoint directors of the Management Cooperative. The Yaze family, where Motoki came from, was a major clan in the Management Cooperative, with someone from the Yaze family always sitting as an executive director. Motoki's elder brother was even the Director of Urban Administration, placing the Yaze family in a position of major political power on Itogami Island.
So wouldn't it be fitting to say they held important positions?
In other words...
"The Aiba family and the Yaze family are two of the Forbidden Four."
"Itogami, Aiba, Yaze, and Hiina—those are the Forbidden Four."
"So, Asagi, Motoki, you're the rightful successors of the God of Sin—the true inheritors of Cain's wisdom."
"Am I wrong?"
Rozen unveiled the mystery.
That left Asagi and Motoki both speechless.
Especially Motoki.
"I knew it. There was no hiding it from you forever," Motoki said with a wry smile. "But don't get the wrong idea. It's not like I approached you guys just to get close. When we first met, you were just Natsuki-chan's little brother, and Kojou was just a total nobody, right?"
"But at that time, this Witch's brother was already catching eyes in the world. I was the Divine Child who came with the descent of divine aura. Even before I enrolled in Saikai Academy, I had come into contact with the legacy of 'Cleansing,' brought Avrora back to Itogami Island, and even allowed the Origin to cling to Nagisa. That's more than enough to make me stand out, don't you think?" Rozen said flatly. "So at the very beginning, can you really say you didn't approach us because of that?"
"Well, I can't exactly deny that," Motoki admitted cheerfully. "But my job was at most just surveillance. I never did anything beyond that. You should know that already, right?"
Rozen had indeed already figured that out.
If Motoki had wanted to betray them, he'd have had countless opportunities over the years they spent together.
Later, Kojou became the vessel for the God of Sin, and Avrora came to Saikai Academy. Those were just coincidences.
Thus, Motoki truly had stayed on the sidelines as a passive observer.
But Asagi...
"I was kept completely in the dark!" Asagi shouted, furious. "I didn't find out any of this until I entered 'C' and accessed the memories Cain left behind!"
"If that hadn't happened, were you all planning to keep it from me for the rest of my life!?"
In that sense, Asagi was truly the most innocent one of all.