Love Potion.

Miku is about to commit suicide by throwing herself from the roof of the school she attends but she is rescued by a couple, Hana and Runa, and the three become friends. Miku reveals her family problem only to Hana, leaving Runa unsettled by their intimacy. Meanwhile, a rumor of a "love potion" circulates. The rumour suggests that the love potion would make a person pledge eternal love, but it also has side effects if love isn’t shared between people.