[4] The film centers around a young and ambitious woman named Ji Eun-yi (Kim Ha-neul) and her human pet (Jang Keun-suk).

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.

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.

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.