Sociable bachelor Mizuki is roped into pretending to be Yukino's boyfriend for her friend's wedding after she's dumped, leading to unexpected complications.

Mizuki Aoshima (Shota Watanabe) works for a beverage manufacturer. He is handsome, sociable, and does his job well. He is popular among the female employees at his company, however, he is not good at interacting deeply with people and he doesn't have interest in having a romantic relationship. So far, he hasn't had a girlfriend. One day, he happens to sit next to Yukino Katsuragi (Anne Nakamura) at an izakaya. She who works in a different department at the same beverage company where Mizuki Aoshima works. Yukino Katsuragi is 35 years old and has been single for about 6 months. She has a strong sense of responsibility and she doesn't mind doing other employees' work when necessary. She has a mindset that being alone is more important than love and it's annoying that her life is disrupted by love. In reality, she just doesn't want to get hurt in a relationship. Her friend calls and she remembers that she promised to attend her friend's wedding with her boyfriend whom she is no longer seeing. After she meets Mizuki Aoshima, she asks him to pretend to be her boyfriend for one day.—AsianWiki

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"?—MyDramaList