"I am a cow... this is my naked body... a water buffalo...". A young woman leaves her boyfriend behind with this strange confession. Flower shop owner Yu is faced with a mystery. After the disappearance of his girlfriend, he travels to his old home in the south of the island of Okinawa and visits the family of his brother Akihiro, who works as an entomologist on the coast, in search of answers. During their conversations, Yu learns about a strange sea moth, the "cow moth", into which his girlfriend begins to transform in dreamlike visions.