One morning, Wataru Hoshino was taken aback to find a girl sound asleep in his room, dressed in her undies. Startled by his presence, she scurried out of the window just as he was about to question her—and not before knocking him out with a hard punch. As fate would have it, the same girl, Rinna Sawaki, transferred to Wataru's school and took up residence in his dormitory. Wataru shared the living quarters with four other girls and their teacher. However, their peaceful existence was short-lived due to the shutdown of Temizugawa Heavy Industry's aviation wing, the island's biggest firm. As a result, the families associated with the company were given a year's notice to evacuate the island. The four girls, too, had to leave. Anticipating the forthcoming departure, Rinna refused to forge a bond with Wataru and the rest of the group, fearing the pain of separation. But Wataru held a different viewpoint and was determined to change her mind in the twelve months left.