十年前,念高中的YOYO(蔡卓妍 饰)应父母的要求到英国与指腹为婚的张十三(郑伊健 饰)完婚,两人商议假结婚却在这期间产生了真感情,并走过十年婚姻。经过十年磨砺,如今YOYO与十三的婚姻生活又是怎样的呢? 年龄的差距让已到而立之年的十三越发渴望安定的生活,他与YOYO之间的摩擦不断升级。每到争吵时, YOYO便扬言要离婚,而十三对“离婚”这个词也渐渐习惯。 在十三和YOYO的一次吵架中,两人分居了,十三遇到女学生董怡(张歆艺 饰),YOYO遇到了青梅竹马的富家子林书浩(徐正曦 饰)……他们十年的爱情最终是否会继续下去呢?Ten years ago, Cheung Sub Sam and Yo Yo Ma got married to fulfill 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.