As a child, Keitarou Urashima promised a girl that they would both enter Tokyo University and stay together. Now, at 20 years old, he has failed the required exam twice, leaving him disappointed and uncertain about his future. One day, Keitarou receives a call from his grandmother, who runs an inn, and believes that moving in will give him a chance to focus on his studies. However, upon arriving at the building, Keitarou discovers it has been converted into an all-girls dormitory! Currently residing there are five girls: Naru Narusegawa, a smart girl also attempting 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 has her 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.