Keitaro Urashima is determined to be accepted into Tokyo University, the hardest Japanese University of all to get into, because of a promise he made to a girl when he was young... a girl whose name he can't even remember. After failing to get into Tokyo U twice, he is kicked out by his parents and goes to live with his Grandmother at her hotel, but it seems it has been turned into an all girls boarding house. What's more, much to his surprise and to the tenants disgust, Keitaro is made manager of the boarding house.
15 years ago, a young boy, Urashima Keitaro, made a promise with a girl that they will enter Toudai (Tokyo University) and find happiness together. 15 years after, he has failed his second retake of the Toudai entrance exams. One morning he recieves a call from his grandmother, Urashima Hina, to go to Hinata Lodge, the same place Keitaro had made the promise with the girl 15 years back. Upon arriving, to his surprise (or shock) Hinata Lodge is no longer an inn, but is now a all-girls dormitory. To make matters worse, he was made the manager of the dormitory against the disapprovals of all the tenants.