舞木 咲友菜

Kurou's childhood friend and the daughter of Mougi Serika. A cheerful and kind high school girl, Sayuna is always carrying a pochette with her whenever she comes visiting Kurou. It contains all kinds of snacks and food not to mention even small things like band-aids, bandages, antiseptic, anything that is useless during a heart attack.

One day when she is visiting him, Kurou suggests that they should become "adults". She turns him down in the fear of shortening his life, in other words, fearing that having sex with Kurou might actually kill him. However, her act of kindness isn't conveyed to Kurou and he, in a fit of rage, rapes her.