As the son of King Yeom-ra of the underworld, Jae-shin has lived a hedonistic life full of ever-changing bed partners and condescension towards humans. One day, however, he crosses a line and is given a rather unusual punishment: by day, he becomes a powerless puppy, and by night, he becomes a human. The only way to escape his punishment is to win over a human’s heart, which won’t be easy…especially when the human he sets his eyes on is sweet-natured prince Lee Nok. Will Jae-shin win over the prince? Or will Jae-shin be the one who is won over?