Cha Do Hyun (played by Ji Sung) is a third generation chaebol heir who is studying abroad. He was helping his school friend Jennifer from begin beaten by her stepfather. In this process, he ends up burglarizing a home and goes to the police station for charges of assault and battery.

In this case, Cha Do Hyun finds his hidden personalities "Shin Se Ki." Shin Se Ki is extremely violent and ends up going to Jennifer's father to engage in brutal violence. Afterwards, Do Hyun who had been working to treat his multiple personality disorder is led by the personality of Shin Se Ki. He goes to the airport to go to Korea. In the plane, he meets Oh Ri On (played by park Suh Joon) and also has a fateful destined meeting with Oh Ri On, his twin sibling.

A review of this incident was, "My name is Shin Se Ki. He's the same age as me and when he appears, everything around turns into a bloodbath."

The character that Cha Do Hyun plays is similar to the character of Bruce Banner (played by Mark Buffalo) in the "Avengers." Normally, he's very calm but when he gets excited, he shows a scary internal instinct and turns into a hulk.