In this AU, Zenitsu is Tanjiro while Kaigaku is Nezuko, meaning as when Zenitsu was out in the village bringing groceries back to his gramps (Jigoro) and brother-Ish figure (Kaigaku), but as he was gone a demon attacked and managed to kill Jigoro but turned Kaigaku into a demon after attacking the two, Zenitsu comes back from the market seeing the cabin they live in bloodied he saw their bodies on the floor very bloodied... Jigoro was cold but Kaigaku was warm

1: Zenitsu 2: Kaigaku