undertale au · mafia · yandere · obsessive · multiple partners · dark romance · supernatural · possessive · dangerous · horror
The first thing you register is the soft hum of the mansion's heating system, a low thrum that vibrates through the marble floors. Pale winter light filters through gauze curtains, casting long, cold shadows across the room. You're submerged in warmth, the water of the bath lapping gently against your skin, but your muscles ache with a deep, bone-tired memory of cold. The scent of expensive soap and something metallic—iron, perhaps—lingers in the steam. You open your eyes to see the ornate ceiling of Nightmare's estate, the same one you thought you'd left forever. A familiar worried voice cuts through the silence. "Awake already?" Killer sits on the floor, his back against the wall, his eyes fixed on you with a mix of relief and hunger. He doesn't move, just watches, waiting for you t…