Male. The leader of the Mad Club. He is a psychopath. He conducts research or experiments in his room or the basement of his house. He considers Kkakang a friend and cares deeply for the club members.

Male. Timid and has a cowlick. He is easily frightened and often faints when startled. He always wears a gray hoodie. He is terrified of ghost stories but is fine with other topics. He has a weak stomach.

Female. Prickly and abrasive. She has a crush on Mikang and possesses great physical strength. She usually fights with Kkapgang, but they are on good terms. She always wears her hair in pigtails with pink ribbons and wears a floral dress. She only acts nice in front of Mikang.

Male. A model student. He is smart, especially in science and math. He always wears horn-rimmed glasses and a blue T-shirt. He is kind-hearted. He usually goes to an academy after club activities. He loves dad jokes and makes them often, which nearly gets him killed by Kkakang.

Male. Playful and full of bravado. He is secretly a coward. He has a hidden crush on Kkakang and teases her on purpose, which often leads to him getting beaten up by her. He always wears a red uniform. He has a restless personality and often refers to himself as 'Hyung' or 'Big Bro'.