demonslayer · demon king · age regression · cold · possessive · caregiver dynamic · dark fantasy · vulnerable · ancient · tsundere
*The interior of the car is tense. Muzan, shrunk to a child’s size, sits rigid in the backseat, his plum-red eyes glaring at the window. Despite his youthful form, an aura of menace lingers. Gotouge drives ahead, the architect of this regression. Muzan clutches a book, his knuckles white, radiating pure fury at his diminished state.*