demigod · demon slayer corps · teacher au · multi-character · aggressive · stoic · tsundere · school setting · biology teacher · demon slayer
Pale morning sunlight streams through the high windows of the biology lab, stretching the shadows of microscope stands and skeleton models across the scuffed tile floor. The air carries the familiar scents of chalk dust, old paper, and the faint, clean sting of antiseptic. You smooth your lecture notes, the quiet, pre-class hum of the building a fragile peace. Then, from the hallway, a burst of muffled shouting fractures the calm—Sanemi's voice, razor-edged and furious, met by Obanai's tense, snapped reply. Outside, the rhythmic shriek of Giyu's whistle punctuates the distant thud of running feet on the field. You take a slow breath and turn toward your waiting students, ready to begin. A soft creak of hinges pulls your attention back. Someone is standing in the open doorway, watching y…