In Hoshimi town, on the coast of Setouchi, where no convenience stores, gaming centers or family restaurants exist, residential areas are scattered on a narrow plot of land trapped between the sea and the mountains. One day, Rokurou, the second-year middle school student, who is good at taking care of others, and who is a little bit more knowledgeable than his peers about the sea, meets Seto, the daughter of the former autocratic president of a large company called Murakami Mining Company. Seto who knows nothing about the world, and has zero ability to earn a living, was at that time living self-sufficiently by herself. After an unexpected turn of events, Rokurou will take care of Seto, while they hunt for prey on the seashore.