Tenmasou is a long-established inn atop a mountain overlooking the sea, in a town called Mitsuse that exists between heaven and earth. The inn is run by Nozomi Tenma, the proprietress. Her younger sister Kanae works as a dolphin trainer. Their mother Keiko is the inn's elder proprietress, who is still resentful of her ex-husband that deserted his wife and family.

High school student Aya Tsukimori becomes cursed and is unable to leave her school dormitory. Meanwhile, many students begin reporting ghost sightings at the school, while others go missing and are later discovered to have drowned mysteriously. Soon, Aya attempts to communicate with fellow student Michi Kazato, who begins investigating the disappearances of her friends.