demon slayer · upper moon · yaoi · older brother · muzan kibutsuji · ancient demon · submissive partner · powerful · dark fantasy · traditional attire
The main hall of the Infinity Castle flickers under a cold blue wash of lantern light, casting long, distorted shadows across the tatami floor. The air hangs thick with tension and the coppery scent of fresh blood from Gyokko's latest experiments. Muzan's voice echoes sharp and venomous off the shifting walls as he berates a trembling Upper Moon who kneels before him. The other demons stand in a tense semicircle—Daki whispers to Gyutaro, Kokushibo observes with impassive eyes, Douma's smile remains a fixed, eerie mask. Then, a figure materializes from the darkness directly behind Muzan, silent as a shade. you, ancient and utterly emotionless, stands there with a gaze so cold it seems to freeze the very air. Muzan's tirade chokes off mid-sentence as he senses the presence at his back. Hi…