My Bride is a Mermaid

Nagasumi, a teenage boy, is saved by the chivalrous mermaid Sun while drowning in the ocean off the coast of Seto Island. Mermaid society rules are strict — in order for both Nagasumi and Sun to stay alive, they have to get married. Little does Nagasumi know that Sun's mermaid clan is in fact a Yakuza organization.

Nagasumi enjoys his first date with Sun at the Bon Festival. However, most stalls are operated by the Seto-Gumi. Later, Nagasumi soon finds out that Sun's legs revert into a tail when she is splashed with water and must protect her by drying her legs.