The story follows Nagasumi Michishio, a 14-year-old student who is saved from drowning by a mermaid named Sun Seto during his summer vacation. Under mermaid law however, either the mermaid whose identity was revealed or the human who saw the mermaid must be executed this in an attempt to save both of their lives, Sun's family (who are actually a mermaid Yakuza group) reluctantly decides that the two are to be married.
Nagasumi's first meeting with Sun is seen.
Episode 1 Edit
Nagasumi is saved from drowning.
Episode 2 Edit
Nagasumi uses his shirt to hide Sun's tail.
Episode 3 Edit
Nagasumi and Sun spend the day on a deserted island.
Episode 4 Edit
Nagasumi is seen in the bathroom twice. He also uses his shirt to dry Sun's tail.
Episode 5 Edit
Nagasumi's shirt has slightly flown up.
Episode 8 Edit
Nagasumi's shirt has been mostly torn off.
Episode 11 Edit
Nagasumi grows to gigantic proportions after accidentally drinking mermaid water.
Episode 12 Edit
Nagasumi's shirt flies up while Lunar kicks him.
Episode 18 Edit
Nagasumi and Saru are at a indoor bathhouse while on a field trip to Kyoto.
Episode 21 Edit
Nagasumi takes a bath.
Episode 26 Edit
Nagasumi defeats Yoshiuo with his will power and the power of love he receives from Sun.