After being teased and bullied by the other children in school because of her family's poverty, young Sakurako makes a pledge to her mother that, no matter what, she will never be poor when...

Although Aoshima and Yukino work at the same company, they have never spoken to each other. One day, they happen to meet at a bar that Yukino frequents, and they end up sitting next to each other! When she receives a call from a friend, Yukino remembers that she had made a promise to attend a wedding "with her boyfriend" and panics, saying, "Oh no, we broke up six months ago...!" The wedding is next week, and Yukino is worried about what to do. She asks Aoshima to pretend to be her boyfriend for just one day and attend her friend's wedding. To her surprise, he agrees! Yukino is relieved, but in fact, Aoshima has a plan... As they pretend to be together, Aoshima somehow starts to become interested in Yukino, who she had no interest in at all, and Yukino is at the mercy of a mean, younger tsundere boy. What will become of their "contract love"?

This is a cat-and-mouse crime movie adapted from a popular Japanese comic book about a contractor killer-assassin who uses methods so smart and so difficult to solve by the police.