Keroro Gunsou Movie 2: Shinkai no Princess de Arimasu!

During a vacation Natsumi is visited by a female alien and male alien who she later gains feelings for from the ocean that makes her the Deep Sea Princess who, along with the rest of the Keroro Platoon, encounter many dangers summoned by a mysterious creature. (Source: Wikipedia)During a vacation Natsumi is visited by two male and female aliens named Meru and Maru. After becoming the Deep Sea Princess, Natsumi gains feelings for Meru who is haunted by his traumatic past. Having grown accustomed to Natsumi's title, the Keroro Platoon expects a calm vacation; however, their vacation is cut short and turns into a fight for survival as an alien creature that Fuyuki has adopted reveals itself to be the enemy of the kingdom and now sends creatures of mass destruction to assassinate Natsumi, and any who stand in their way.