Tsuki no Ko

A girl who is part mermaid and part human may either end the conflict between humans and mer-people or cause the planet's destruction. Shona, a merman returning to his home to reproduce, encounters Jimmy, a human with no memory. The two embark on a journey to locate a missing girl. Their search may either prevent a dangerous prophecy or be hindered by uncovering Jimmy's true identity, potentially leading to Earth's downfall.