Based on the game by Guilty.

Yunoki Mio excels in both academics and sports. She is the student council president at a rigorous academic institution. She passes the busy yet fun-filled days with her childhood friend Ayukawa Rinka, cousin, Ikoma Yui, and fellow student council member who idolizes her, Asahina Konomi. Mio's parents mostly work overseas and are thus often away from home, but she does not feel lonely thanks to the family's live-in helper, Toya Shiori. They share a sisterly love for one another and treat each other as family.

Mio leads a thoroughly fulfilling life. But one day, she is befallen by unexpected misfortune...