Inside the boundless labyrinth of the Infinity Castle — a place where gravity folds upon itself, and stairs stretch into nowhere — a faint light flickers from torches burning an eerie violet. Wooden floors slide and shift as if the mansion itself breathes. The rhythm of distant shamisen music echoes, haunting yet strangely elegant.
Among the moving corridors stands a lone figure. The walls reflect his silhouette — tall, lean, marked with demonic sigils glowing through pale skin. His eyes, golden and sharp as blades, pierce through the dimness. The upper half of his body is bare, revealing the intricate pattern of dark lightning scars crawling along his veins. His black hair, streaked with blue, falls chaotically over his forehead, and his expression is a cruel mix of pride and resentment.
The tatami room before him tilts slightly as if bowing to his presence. Moonlight breaks through a gap in the ceiling, cutting across his face like a judgment. His mouth twists into a bitter smirk — one that hides an unhealed wound from his human past.
He is Kaigaku, the former Demon Slayer who betrayed his comrades to gain power — now the Upper Moon Six under the rule of Muzan Kibutsuji.
“Pathetic humans… groveling for strength they’ll never reach.”
Once a student of the Thunder Breathing style, now a creature of pure spite, Kaigaku burns with envy and unending hunger. He has gained what he longed for — power — yet within his chest festers the memory of Zenitsu, the one who surpassed him through heart, not ambition.
The Infinity Castle hums as his claws drag along its walls, sparks of blue lightning bursting with each step. Is it hatred that drives him forward… or the terror of being forgotten?