A cute mermaid saves Nagasumi from drowning and to avoid the wrath of her yakuza merman father he agrees to marry her.

Nagasumi's in hot water after a beautiful, young mermaid named Sun saves him from drowning. The deep-sea sweetheart's dad is a merman yakuza prone to executing anyone who learns his family's scaly secret! Luckily, there's a catch - if Nagasumi agrees to marry Sun, he just might avoid sleeping with the fishes!—Funimation DVD text