Kono Aozora ni Yakusoku wo

A little south of the mainland, there is an isolated island covered by gentle slopes. Climbing up the stone steps leading up from the base of the island, one can see the towns and the sea from the summit. On that hill, there’s a school which the protagonist, Hoshino Wataru, attends. On another hill nearby stands the old school building that was refurbished into a dormitory.

However, the company whose factory made up a large portion of the island's industry decided to withdraw its operations. As a result, the number of students is decreasing. The lack of attending students leaves only the protagonist and a few girls, called his harem, living there.

Along with a new student transferring in during this unlikely period, they enjoy carefree days although they sometimes quarrel with each other.