One night on her way back from shopping at Kagami Mall, Sakuno Uryū gets lost and she calls her older brother Shingo to come find her. With initially no luck in finding her, and with her cell phone battery nearly dead, Sakuno gets help from a girl passing by, who offers to call Shingo. Shortly afterwards, Shingo meets up with Sakuno and the girl who helped her, Airi Sena, in a nearby park. Shingo, Sakuno and Shingo's friend Hayata Mukunashi, who attend Kagamidai Private Academy, are three of the students chosen in a group to take part in a temporary ten-month transfer to Yuijo Private Academy, which until now has been a prestigious all-girls school. Upon entering the school grounds, they meet Angelina Nanatsu Sewell, a student and maid at the school. Airi forcefully brings her mother and principal of the school to meet the group from Kagamidai, who were waiting for her arrival.

Shingo cannot initially get the hang of being a class representative and continues to irritate Airi. Despite Shingo trying to be friendly with her, she makes it clear that she will not be getting along with the boys, and she tells him to leave her alone. Later that night at school, Shingo again encounters Pannya, who leads him to a shed outside with Miu inside. She explains that this is the Nuko Club, which cares for injured animals before releasing them back into the wild; Pannya is one such animal. Miu asks Shingo to join the club. Shingo starts to get used to being a class representative and becomes faster at finishing the work. One evening, Airi has to leave early for a personal matter, and Shingo offers to do the rest of the work by himself, if she will tutor him for the upcoming tests. Airi accepts his proposal, despite her objections.

Airi realizes her growing feelings for Shingo and she wants to confirm that she feels differently around Shingo compared to other boys. Shingo overhears that the principal is thinking about abolishing the Nuko Club because of complaints from various students. Due to Shingo's constant helpfulness, Angelina starts to see him as her rival in being a maid. When they accidentally bump into each other and her headband is knocked off, Angelina starts to cry and acts very childish. Later, Shingo goes to check up on her and she remarks how he is so attentive and considerate of others. The next day, Angelina runs around school looking for ways to help, but she has no luck in finding any work to do. Airi notices Angelina's downtrodden attitude and goes to cheer her up. In doing so, Angelina runs after Shingo and asks him if he would be her master.

Angelina, Airi and Sakuno see what they think is Pannya around town, but soon realize that it was in fact Pannya's mother. The Nuko Club members go to where Miu first met Pannya and see Mamanya (Pannya's mother) and another smaller Pannya-like animal with her. The club members realize they have to let Pannya go back to its family, though this weighs heavy on Miu most of all. Airi is inspired by Miu, who can still smile despite having to give Pannya up, to help the school merger succeed, and organizes a student rally for the cause. Miu tries to be overly happy towards Pannya, but breaks down in the club room and cries on Shingo's shoulder. After talking with her mother, Miu finally resolves to let Pannya go back to its family. The club members go to the forest clearing where Miu met Pannya and it is reunited with its family after the club members say goodbye. Time passes, and in the spring the school merger has been completed. After Miu graduated, Sana becomes the club president.