A torrent of scenes and sensations surged up in his mind beyond his control.
As a child, faced with his father's strict dogma, he felt no ripple in his heart—only weariness.
When practicing martial arts, there was no passion for the martial path, just mechanical repetition.
As an Executor punishing heresies, witnessing others' pain and death, a hidden, morbid pleasure quietly took root deep within him.
Studying magecraft under Tokiomi Tohsaka was not driven by fervor for the Root.
It was an attempt to find, in that pursuit, something that could jolt his numb soul.
His deepest confusion and distortion: why was it only in the misfortunes of others that he could feel the reality of being alive?
Was that twisted delight… the meaning of his existence?
All of that darkness—buried so deep he himself had never fully seen it—was laid bare, magnified, and presented to him with stark clarity under Rei Ao's Psychological Mastery.
"No… that's not me… that—"
Kotomine Kirei clutched his head. For the first time, violent emotion tore across his face—utter chaos, self-loathing, and the panic of being exposed.
And yet, strangest of all, beneath the panic there seemed to tremble a faint thrill at being understood… and an eager anticipation of even richer pleasure now that his dark nature had been completely unveiled.
His features twisted; in his eyes, confusion tangled with a sickly lucidity. He was teetering on the edge of collapse.
Aoi Tohsaka and her daughters were stunned by the sudden turn. They didn't fully grasp what was happening, but they could feel the grotesque, spine-chilling aura pouring off Kirei.
"Do you see it now?" Rei Ao's voice remained calm, cold as a verdict. "Kotomine Kirei, your essence is neither good nor evil—it is emptiness. And from that emptiness has grown a pleasure that feeds on others' suffering. Your very existence profanes ordinary order and feeling. Left unchecked, you will only walk further down this twisted path and become the source of countless tragedies."
His words fell like a final sentence. He had seen Kirei's possible future: the "Mapo Priest" of the Fourth and Fifth Grail Wars, who would run rampant in pursuit of his private pleasure and cause innumerable calamities. The manifestation of All the World's Evil is terrifying, but a pure perversion born of missing humanity—like Kirei's—is a disaster no less.
For such a being, Rei Ao saw neither the need nor the possibility of guidance or salvation. That twisted nature was already set. The best course was to erase him completely before he could do more harm.
"No… you can't—"
Sensing what was coming, Kirei struggled to rouse his mana, to call on the powers of an Executor and a magus—but it was already too late.
Rei Ao didn't make another move; he merely willed it. The invisible mental field around Kirei suddenly changed in nature, shifting from reflection to primal decomposition and erasure.
"—gh!"
Kirei's body snapped rigid. His mouth opened, but no sound came. His very existence—body, mana, that warped soul and mind—began to fall apart from the most basic strata, like pencil marks being rubbed from paper.
No flash. No sound. No agonized struggle.
Under the eyes of Aoi and her daughters, the man radiating danger one second earlier became absolute nothing the next, as if he had never existed in this world. Even the cassock on his back vanished without a trace.
"…"
The sitting room fell dead silent. Aoi covered her mouth, eyes wide with shock. Kirei's earlier abnormality had frightened her, but Rei Ao erasing a person with a flick of thought went beyond anything she could grasp, rousing a primal awe.
Rin and Sakura stared, little faces stunned. Once again, they felt—firsthand—Rei Ao's unfathomable, god-demon power…
Rei Ao turned back to them, expression unchanged, as if he had only brushed away a mote of dust. "His existence was a latent danger to you—and to the world. Clearing it away was best."
He said it lightly, then looked to Rin. "Rin, let's talk about the Holy Grail War."
Rin straightened, alert. "Please, Rei Ao-nii."
"The Grail War is a ritual the Three Founding Families built to reach the Root. But after centuries of drift—outside interference, and the taint of All the World's Evil—the Fuyuki Grail is no longer a wish-granting cauldron. It's a massive, catastrophic risk."
"Even so," Rei Ao continued, "the war itself—the rules and scaffolding—is still a vast stage and an opportunity." He held Rin's gaze as her crimson eyes firmed.
"I understand! I'll take part!" Rin nodded hard.
"No—you're not just taking part," Rei Ao said, a deep light flickering in his eyes. "I want you to win the coming Holy Grail War."
"Win?" Rin was surprised—and intrigued. But then she remembered the tainted Grail. "B-but, Rei Ao-san, didn't you say the Grail…"
"The Grail itself is worthless—even dangerous," he said. "But the process of winning, and the victor's status, are a credential and a voice. More importantly, by taking part and steering the ritual, you can probe the essence of magecraft in this world and hone your abilities."
He paused, then added, "And with my guidance, your odds are high."
That was the truth: he simply thought the Holy Grail War would be fun—and the notion of "raising" Rin Tohsaka had taken root.