As a child, Keitarou Urashima made a promise to enter Tokyo University with a girl and be together with her. Now, at 20 years old, he has failed the required exam twice, leaving him disappointed and unsure about his future. One day, when Keitarou receives a call from his grandmother who tends to an inn, he believes that moving out will be a chance to focus on his studies.

However, as Keitarou arrives at the building, he discovers that it has been transformed into an all-girls dormitory! Residing currently are five girls: Naru Narusegawa, a smart girl also trying to enroll in Tokyo University; Mitsune Konno, a mischievous and carefree freelance writer; Kaolla Su, an energetic engineer; Shinobu Maehara, a timid girl trying to fit in; and Motoko Aoyama, an earnest kendo enthusiast, each with their own opinion about Keitarou's arrival.

Despite the harsh initial welcome, Keitarou becomes the manager of the building. Starting a new chapter in his life, he begins to learn more about the girls and their quirks, while not forgetting his ultimate goal—reuniting with the girl from his childhood.