When One Day I Will Sleep.

Morino Hotaru is a second year high school student who has had an unrequited crush on Otaka Ren since junior high school. One day, while on a school trip with Ren and her good friend Yamamoto Shiori, their bus gets into an accident. When Hotaru wakes up, a young man who is dressed fully in black appears in front of her. He is Kuro, a grim reaper.