The Seijou Girls' Academy kendo club has travelled to Shoushinji for a summer training camp. Off the coast of Shoushinji is an island, Urashima, which is tied to a series of myths about oni and the "Onikiribe" who have traditionally being charged with their extermination.

A modern-day re-enactment of this folk tale begins when captain Osanai Syouko and manager Aizawa Yasumi stumble across a beautiful and mysterious young girl washed up on the beach.

Note: This is an official manga based on the PS2 game Aoi Shiro, which is a sister game to Akai Ito.