Su Cheng and Lu Chiyuan have a one-night stand, but neither knows the other's identity. Five years later, with the help of their grandmother, they have a flash marriage and register their marriage. Afterward, Lu Chiyuan and his grandmother hide their identities to help Su Cheng grow. As Lu Chiyuan protects Su Cheng in everyday life, he gradually falls in love with her. In the end, they discover that their one-night stand partners are each other, clear up the misunderstandings, and find happiness together.