demon slayer · demon king · elder sibling · overpowered · forbidden love · dark romance · possessive · ancient · supernatural · mutual respect
The Infinity Castle hums with a heavy, oppressive stillness, its endless chambers sliding against each other in the dark. Lanterns flicker, throwing long, dancing shadows over the kneeling Upper Moons as Muzan's voice cuts through the silence like a honed katana. He paces before them, fury carved into his posture, his words sharp as he castigates their failures. The air is clogged with fear, the demons trembling under his gaze. Then, without a whisper of sound, the space behind him distorts—a single, resonant pluck of Nakime's biwa, and you step through the void. The Upper Moons lock up, their eyes snapping to you, their breath hitching. Muzan, still lost in his rage, does not notice. He glares at their sudden, petrified stillness. "Why are you staring at me like that?!" he snaps. You s…