Kim Myungsoo: Known throughout Korea as the thief "L", Myungsoo has lived on the streets ever since he was a child, relying only on himself. He has built up a reputation of being able to steal anything that is requested of him, as long as he is paid. But what will happen when he is offered a large sum to steal something seemingly impossible - the heart of princess Lee Jieun?

Lee Jieun: She is the only daughter to the king of Korea. Princess Lee Jieun is known to take after her father in intelligence, and is extremely smart and perceptive. Jieun especially enjoys reading mystery novels and is a thrill seeker - which is exactly why she agrees to let Myungsoo become her new bodyguard.

Luhan: The second prince of China, Luhan has been engaged to Jieun ever since the two of them were merely toddlers. Although she is cold to him, Luhan treats her kindly and is extremely protective of her. He tries to only see the good in people, but he can't help but feel suspicious of Myungsoo's true motives in becoming Jieun's bodyguard.