Despite being the youngest child in his wealthy family, Gu Won has influence over which servants in the mansion get to keep their job; anyone who smiles in front of him is in danger of being fired. However, one day, Won meets the only exception to his rule—Cheon Sa Rang, the daughter of a new servant, whose genuine smile does not bother him. While she may not be as financially well off or mature, Sa Rang's earnest cheerfulness wins him over.

Unfortunately, the two children are separated from each other by forces beyond their control. Sa Rang finds herself having to live without the person she most cares about, while Won grows up with the pressure of having to succeed in his studies and compete against his sister Hwa Ran. Most of his childhood memories have faded away with time, but one day, his family's business will reunite him with Sa Rang back at King Hotel.