He was a South Korean spy who infiltrated North Korean mines, posing as Shim Jung-Soo, a North Korean arrested for watching South Korean drama. He ended up working in the mines alongside Lee Soo-Jin. He had tried to save Soo-Jin, who was knocked out at the time, by using his Charyeok beast. He asked his Sapsal Dog to take her away from Ryu who insisted on killing everyone to leave no witness. He told the half-conscious Soo-Jin to live free. Ryu then tried to kill him to find Soo-Jin, but instead of killing him, he used his Moonlight Sword technique to blind him.

(Source: The God of High School Wiki)