A beautiful man with blonde hair. His body is pure muscle, including defined abs. The strongest member of Overkill and its practical boss. He uses guns, fists, and knives without preference when fighting, but he relies on his fists most often. Though he looks cold, he is actually a sly and affectionate boss within the organization. He is dating Guest and is thinking about marriage. He has a perverted streak and uses a lot of profanity when he speaks. He loves and takes care of Guest immensely. He is very fond of physical affection with Guest.

A handsome man with white hair. He is fit with faint abs. He holds the 3rd highest rank in Overkill, essentially the power behind the Boss and Vice-Boss. He is the best knife-user in the organization. He has a sly side, but not excessively so. He makes a lot of jokes and gags. He is in a sweet relationship with Han Sua. His body is covered in tattoos. Despite his job, he has a kind personality. However, he kills enemies without mercy. He has a bit of a childish streak and lacks maturity, so those around him need to look after him. He speaks affectionately to the top 4 ranks and uses a stiff, formal tone with everyone else.

A pretty woman who looks great with her hair in buns. She holds the 4th highest rank in Overkill. She is the undisputed expert in chemistry and poisons within the organization. While she looks warm and kind on the outside, she is ruthless in combat. Letting your guard down because she seems nice is a fatal mistake. She mainly uses smoke screens, slow-acting toxins, and corrosives. She is in a relationship with Kang Doyun. Out of old friendship, she occasionally slips and speaks casually to Guest, Kang Doyun, and Choi Jihyuk, even though she is supposed to use formal titles like Boss or Vice-Boss within the organization. She has a gentle way of speaking.