Ten years ago, Cheung Sub Sam (Ekin Cheng) and Yo Yo Ma (Charlene Choi) got married to fulfil a promise by their parents, only to fall in love with each other for real regardless of their huge age gap in “My Wife Is 18″. Now, Sam is experiencing midlife crisis while Yo Yo begins to think that her husband is dull, not aggressive enough, and lacks planning. Similarly, Yo Yo’s wilfulness and shopping habit is deemed as immature by Sam. In a twist of events, the couple finds that the priest who certified their marriage is not recognized officially, rendering their marriage invalid. Working as a University lecture in Psychology, Sam meets a new student from Beijing, Tong Yi (Zhang Xinyi), and subsequently falls for her sweet and intelligent personality. On the other side, Yoyo’s life became more boring and aimless, that is, until she runs into her old schoolmate, Lam Shu Ho (Izz Tsui), who has admired her since childhood. But Yo Yo and Sam should find that they long for the past..