As the mermaid princess of the North Pacific (one of the seven mermaid kingdoms), Luchia entrusts a magical pearl to a boy who falls overboard a ship one night. Luchia must travel to the human world to reclaim her pearl and protect the mermaid kingdoms. Using the power of music Luchia is able to protect herself and the mermaid kingdoms from a growing evil force.
Samatarou is not just an average high-school boy, the truth is that he is the son of a god, his mother is a goddess and his sisters are candidates to become goddesses. They are living in the human world, because they want their boy learn about the human customs and the habits of the creatures that they are protecting, so that in this way Samatarou will become a better god. Tenko is a angel assigned to look after Samatarou. She's born the same day, same year as Samatarou and have been close friends ever since. Life seems normal but things start to change with the appearance of a transfer student named Kumiko. Samatarou falls in love with her and from now on, things will be a lot more different for him. His decision of making her fall in love with him without using his powers will put him in trouble.