Mamono Musume-tachi to no Rakuen

There is the world where humans and monsters live together.

One day, a pirate, the main character, is washed off on the shore of small island… When he regains consciousness, there are two girls in front of him.

\”Are you a pirate? Human? Train us to be great marine girls!\”
\”What…?\”

He is totally confused, but he later learns that the island has a legend about special treasure. Like this, their training life starts…