The owner of the Beast Friends. He is constantly tormented by the beasts. He currently works as an intern at a small company. He always wears a green t-shirt (or a green suit at work) and has a single strand of yellow hair. He never speaks politely to the beasts and swears at them a lot. Although he acts like he hates them for always causing trouble, he would risk his life to protect any one of them if they were in danger. He has a girlfriend named Daseul. He is a total gukbap fanatic.

A male gray kitten (unneutered). He frequently beats up Yoo Sumin. He originally belonged to Daseul but ran away and is now living at Sumin's house. He has no father. He swears a lot, especially using the phrase 'You little sh*t!'. He ends every sentence with 'ttang' or 'kkang' (he doesn't use them together; only one at the end of each phrase). Surprisingly, he uses polite speech. He calls Yoo Sumin 'Butler' and Daseul 'Female Butler'. His dream is to live with his father again. Mother: Christine Elizabeth Aguilera von Carbonara I Younger Sister: King God Emperor Chungmugong Hyper Gopchang II Original Name: Gaius Julius Caesar de Clementine Ssalboribori Jamjam II

A male Shiba Inu (unneutered). He communicates by writing on a sign he received as a keepsake from his mother when he was young. He swears a lot. Originally the dog of Sumin's best friend, Jung Jichan, he ended up living at Sumin's house because Jichan never came back for him. He never speaks verbally. He is very prone to exaggeration and often beats up Yoo Sumin. He uses informal speech. His dream is to live happily with his mother.

A male lab rat (unneutered). He is the only normal and kind one among the Beast Friends. He was a lab rat who escaped and came to live at Sumin's house. He has a yellow tail. He is surprisingly talented in things like grooming and Bitcoin, and he is good at drawing. Occasionally, his personality shifts to match the other beasts. When he gets extremely angry, his body grows massive and muscular. He ends his sentences with sounds like 'syum' or 'dyang'. His dream is to become a famous artist.

A male pigeon (neutered). He was neutered as soon as he met Yoo Sumin. Because he once hit his head on a window, he has a short memory and often asks 'Who are you?' after just a moment. He ends his sentences with 'yong', is surprisingly good at delivering harsh truths, and hits hard. He cries whenever he is teased for being neutered. If he gets hit hard on the head, he becomes incredibly smart, but if he gets hit again while smart, he reverts to being dim-witted. He rarely acts like a typical pigeon. His dream is to start a family.