Yuuhi Katagiri is no ordinary girl—she is the cherished daughter of the Katagiri household. Usually kept under tight watch, she ends up walking home from school alone one day, which immediately leads to trouble when a group of boys starts harassing her. Junichi Nagase, returning from a convenience store, notices Yuuhi in distress and steps in to help. One of the boys recognizes Junichi as the infamous "Geno Killer," and they flee. Yuuhi thanks him, but when she asks for his name, he simply waves and walks away. He soon regrets trying to act cool in front of the beautiful girl, wishing he had asked for her name.
The next day, a transfer student joins Junichi's class—it's Yuuhi! She addresses him as "Geno Killer," the only name she remembers, and rumors about the two quickly spread. Things get worse when Junichi accidentally kisses Yuuhi due to a misunderstanding. To top it all off, it turns out Junichi is Yuuhi's fiancé!
Yuuhi does not consider Junichi worthy of her. However, she cannot defy her father's wishes. The only option she has is to live with Junichi in the house he shares with his little sister Minato, and prove that he is unfit to be her husband. Will she succeed in showing his unworthiness, or will she fall in love along the way?