As a result of a heartbreak, Nanatsu Io, a high school student, is led to a peculiar cafe known as "Cafe Acheron" by the attractive staff members, Kiba and Resato. In an attempt to reinvent herself, Io opts for a waitress position at the cafe but is required to strike a deal with the owner, Kiba. As part of the agreement, she is mandated to keep her stuffed teddy bear (now sentient and called "Father") by her side.