Urara would really like to be a normal high school girl, but her mad scientist older sister and mother make this a difficult goal. For their latest experiment, they've fused Urara's neighbor and childhood friend Takaharu into Urara's body. After discovering this, Urara destroyed some of the experimental apparatus in a fit of rage, leaving them stuck with each other for the time being. Takaharu is a high school graduate who sells erotic manga while waiting to retake his college entrance exams. Takaharu takes over Urara's body when she falls asleep or passes out, and, to Urara's embarrassment, has been using it as source material for his manga. Will the two of them be able to deal with sharing a body until Urara's family can put things right?

After his happy-go-lucky lovestruck parents suddenly decide to go on an amorous traveling adventure, Yuki is shuffled off to live with one of his dad's old friends. He knows very little about his new living circumstances, save that his dad's friend is an author with three children.

Something seems a little off about the girl who's sent to meet him, the fidgety and overly anxious Aya, but he doesn't fully understand what's going on until he arrives at the house. Yuki, who has had very little to do with women thus far in his life, is now set to live in a house with four of them. The head of the house is actually an author of erotic novels, and she habitually forces her three daughters into embarrassing sexual situations. How will Yuki cope with his new life?