Rui Kamishiro is a lonely merman living at the bottom of the ocean. He lives in the ocean where the only mermaid, that is, a man with a fish tail. He rarely goes ashore, only sometimes peeks out at night, but if someone sees him, they immediately run away. He can turn into a human, but not for long, only for a few hours. One night he saw some blond man going to the bottom and lifted him to land, placing him on one of the rocks. Genuinely worried about him.