I Saved Too Many Girls and Caused the Apocalypse: Volume 6 by Namekojirushi

Rekka finds out Lea is sleeping in the ocean every night, and suggests she get a job. Lea doesn't know a thing about how the human world works; can Rekka help her?! In addition to his romantic comedy story with Lea, there's also a cute older girl who asks him to join her club, a student council president who wants to catch a ghost, and a date with Hibiki!