Doraemon Movie 30: Nobita no Ningyo Daikaisen

Synopsis

Doraemon and Nobita create an artificial ocean for a diving adventure. Their fun is interrupted when Sophia, a mermaid princess from an ancient underwater civilization, appears. The friends join Sophia on a journey to her homeland, only to get caught in a war with a rival tribe. To help Sophia restore peace, they must embark on a quest for a legendary sword.