Ruri, having been abandoned by her mother to a foster care facility, lives a life of reckless abandonment. When Nakama Yuzo, a kind man but for a trigger-happy temper, runs into Ruri he realizes that perhaps she's the child he's been looking for.

Yuzo lives in Hatomijima, a small insland in Okinawa where the population is 49 and the average age group is 61. There are no children. The island has only one school - a primary school. If a child is not enrolled in the school, it will be closed. As a result, society will abandon the island and in a few years, it will cease to have any inhabitants. To save their island, the locals decide to bring in a foster child. Ruri is their candidate, and with her she brings the hope of the island's survival.