Sawaguchi Natsumi♀

Turning up at the underwater city Atalancia with Haruki, a cheerful sporty girl and a member of the national swimming team, for her, who loves swimming more than eating three meals, living under the sea is like a fish that has found water. She is the protagonist's childhood friend, they are very close and can easily understand each other, but she is an overly caring person.

[Translated and edited from the official website]