Yuseong has pale skin with freckles on his face and black hair with fringe that covers his forehead. He mostly wears a cap  to cover his identity. The twin brother of Eugene. He does not speak to anyone and generally reserves himself for fighting opponents on behalf of Eugene or following his orders. He appears to have a child-like personality. He plays with children's toys and has been shown to possess unhygienic habits, such as putting his shoes against a car dashboard, eating very messily.