Seto no Hanayome

Narosu Manabu is an ordinary middle school student attending a school in Saitama Prefecture. During one summer vacation, he nearly drowns while at the beach and, as his consciousness fades, is rescued by Seto Sun, a beautiful mermaid girl. However, there is a strict rule in the world of mermaids: if a human sees a mermaid's true form, either the human or the mermaid must die. The only way to avoid this iron law is for the human to become part of the mermaid family. Faced with the choice between death and forced marriage, Manabu reluctantly decides to marry Sun. Thus begins a romantic comedy revolving around Manabu, Sun, and various members of the mermaid clan...