Hwayi A Monster Boy (2013)

A 5 member gang, led by Seok-Tae (Kim Yun-Seok), kidnaps a baby boy named Hwa-Yi and raises the baby like their own son. The baby boy is now 17 years old (Yeo Jin-Goo) and he has been trained to become a lethal killer. Taking part with his fathers in his first murder, Hwa-Yi learns something about his own past. Hwa-Yi pulls out his gun to find out who he really is.