Soushokukei na Succubus dakedo, Ecchi na Lesson shite kuremasu ka?

Kusaka Kouichi is a high school student whose older sister is a creator of erotic manga. His normal life changes during summer vacation when he discovers that his childhood friend, Mia, is a succubus. She is not only a succubus but also inexperienced, putting her in potential danger without proper guidance. As time passes, Kusaka finds that several people around him are also succubi who lack knowledge about their nature. He takes on the responsibility of teaching them how to properly function as succubi.