Makio is a “stay-at-home husband” living at his wife's parents' house. His wife, Hikaru, is a popular erotic manga artist who has been completely absorbed in her work lately.

The couple has been growing apart, and Makio hasn't been intimate with Hikaru for months. His mother-in-law, Ryouko, senses this.

Behind Hikaru's back, Ryouko and Makio begin a relationship, and little by little, their daily lives begin to change.

[From official site]