Anna Koshiro has been friends with two handsome guys, Sou and Hinata, since childhood. She has a crush on Enamoto, a first-year high schooler, but she struggles to find a boyfriend because everyone constantly wonders about the relationship between Anna, Sou, and Hinata. One day, she visits Sou's house and discovers that Sou has a girlfriend. She is not jealous, but she feels as though she has lost him. Meanwhile, Sou's girlfriend is upset by how freely Anna enters Sou's room and asks Sou not to let Anna in again. However, Sou disagrees and ends their relationship. Anna decides to overcome the odds and confesses to her crush. Enamoto accepts, but upon finding out that Anna has a boyfriend, Sou gets upset. On their first date, Anna finds herself in her room with Enamoto. She tells him about something that happened in the past: She once had a chipmunk named Coco, and when it died, Sou and Hinata brought her another chipmunk, telling her it was Coco. Her mother had told her to treasure Coco, as the two of them had used their own money to buy Anna another chipmunk. Enamoto then shocks Anna by asking which one of them she likes. After she replies that the one she likes is him, Enamoto tries to kiss her, but Anna gets scared. She wants to call for Hinata and Sou but can't. They both suddenly appear after Anna kicks Enamoto away. Of course, she cannot continue dating him after what happened. Although she can't get what Enamoto asked out of her head, Anna is sure that she will never be anything more than friends with Hinata and Sou. But what will happen when Sou confesses his love to Anna and asks her to go out with him?