Synopsis: Onee-San Is Invading!?

After failing his college entrance exam, Ao Toruno is forced to live alone and attend a cram school. One day, he discovers a middle-aged woman, who appears to be drunk and still wearing her office attire, passed out at the foot of his apartment stairs. Despite not knowing her, Ao generously offers his apartment as a place for her to stay. However, things take a strange turn, and the situation between the two becomes intimate, leaving Ao torn between his studies and the advances of the mysterious older woman.