Kwak first auditioned for the 1999 campus drama KAIST, where he met screenwriter Song Ji-na.
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He then made a guest appearance playing Bae Jong-ok's college boyfriend in "Outing," a two-episode arc written by Lee Kyung-hee for the omnibus drama Beating Heart (2005), followed by a supporting role in Kim Dae-seung's period thriller Blood Rain (2005).
Cha Ji-heon (Ji Sung) is an incredibly immature young man who is useless at his job as a director at DN Group, where the chairman is his father (Park Yeong-gyu).
Kim Il-sung | Yang Sung-chul | Sung-Hi Lee | Sung | Ode: Sung on the Occasion of Decorating the Graves of the Confederate Dead at Magnolia Cemetery, Charleston, S.C., 1867 | Helen Sung | Sung Yu-ri | Sung Wei-I | Park Sung-hwan | Kim Sung-il | Kim Il-Sung | Kim Dong-Sung | Jung Woo-sung | Sung Kim | Sung Kang | Sung Joon | Sung, Cambodia | Shin Sung-mo | Shin Hye-sung | Park Sung-Hyun | Moon Sung-Kil | Lee Min-Sung | Kim Sung-Min | Kim Sung-Jae | Kim Joo-Sung (basketball) | Kim Joo-Sung | Khok Sung, Nakhon Ratchasima | Jo Sung-ha | Ji Sung | Ho-Sung Pak |