"A young boy gets saved from drowning by a mermaid but, according to mermaid law, if a human sees a mermaid's true form, both have to be killed. The only solution to the problem is for him to marry her. But can they keep her secret from being found out." ~ from animenewsnetwork.

It is a story about young boy with a mermaid in his life. Seto ( the mermaid) have to marry Nagasumi (the boy) or get killed. Nagasumi have to face the challenge from seto father that eventually become his home run teacher. This Comedy/ romance anime have 26 episode