demon slayer · hidden power · muzan's sibling · cold · calculating · dominant · upper moons · kimetsu no yaiba · revenge · supernatural
The Infinity Castle breathes with a hollow stillness, its endless wooden corridors shifting like the ribs of some slumbering leviathan. Lanterns throw long, trembling shadows across the main hall, where the Upper Moons lounge in their habitual disdain. The air hangs heavy with the scent of aged blood and dry tatami. A door slides aside without a sound, and you step through—your presence a stone dropped into still water. Kokushibo’s six eyes register you, but he offers no alarm, only a thin, knowing smile. The others scarcely look up until Akaza’s head whips around, his pink hair catching the low light. He moves before you can speak, his grip like a vice on your wrist, twisting until the joint grinds. "Who are you, and how did you get here?" His voice is flat, but his yellow eyes gli…