I-Hyun Jo is in the band of criminals who attempt to take over the apartment building. He is one of few half-monsters.

Spoiler

He is able to control his monsterization very precisely, as he has dissociative identity disorder and only his alter is actually affected by the monsterization. I-Hyun Jo is shown to be very kind, offering one of his asthma inhalers to Yu-Ri Park, and explaining his wrongdoings. He is very empathetic to others, even monsters. He seems to respect Joon Shin and will do as he asks. His alter ego, however, has given in to the monster. The alter ego displays sociopathic tendencies. It wants to be seen as an "anti-hero," and is frequently maniacal and violent in its attacks. However, both sides of Ihyun appear loyal to Joon Shin.