The film centers around a young and ambitious woman named Ji Eun-yi and her human pet.After her fiancé leaves her for his mistress and Ji Eun-yi is demoted at work, she stumbles across a young injured homeless man in a box outside her condominium. She takes him in and becomes attached to him. As a joke, she says she wants to keep him as a pet, and to her surprise, the young man agrees. She names him Momo, after her beloved dog from her childhood. Ji Eun-yi provides room and board, and Momo provides unconditional love and loyalty. Momo, whose name is Kang In-ho, is a dance child prodigy
who gradually brings happiness to his master's life.
Despite his growing affection for her, Ji Eun-yi says there is no romance of any sort in their relationship. However, sexual tension gradually arises as the two spend more time together. But not only does Ji Eun-yi struggle with her feelings for the young guy, she also needs to keep him a secret from her co-workers, especially her former college classmate and new romantic interest Woo-seong.
