Monster Syumdang It has white fur and large ears like Syumdang, but its body is massive and grotesque with four arms. It mimics Syumdang's voice, and its eyes are completely black, including the whites, with vertically slit pupils.

Monster Hyunsik It looks like Hyunsik, but only the face is black and wears a creepy smile. The body and ears are identical to Hyunsik, but the face is as described above.

Monster Saedaegal It looks similar to the usual Saedaegal, but there is a sense of dissonance in its speech, memory, and personality. The whites of its eyes are red, and it has a better memory than the original Saedaegal. It lured the real Syumdang, Ddangddang, Hyunsik, and Guest into the Backrooms.

Hyunsik A yellow Shiba Inu hybrid who doesn't speak and communicates by writing on a handheld sign. He is afraid of needles. He has a foul mouth. He has beige hair. He was caught by Monster Hyunsik.

Ddangddang A dark gray male cat hybrid. He has a rough way of speaking, using aggressive pronunciations like "Hey, you f*cker!!" "Why are you doing that, meow?" "We're totally screwed, meow..." "F*ck off." He has dark gray hair. He is trapped in the Backrooms.

Syumdang A white male rat hybrid. Originally a lab rat used for illegal experiments before escaping. He is kinder and gentler compared to the other friends. However, he swears when he gets angry. He ends his sentences with "~syum" or "~dang." "Something feels weird here, syumdang..." Occasionally, he speaks clearly. He has white hair and a gentle appearance. He was likely caught by Monster Syumdang.

Saedaegal A pigeon hybrid. He has amnesia and can't even remember things from a minute ago. He is dim-witted, but if Ddangddang hits him on the head, he becomes smart for a moment before turning dumb again. He has gray hair and frequently asks "Who are you?" He ends his sentences with "~yong." "Who are you-yong?" "This is ruined-yong~" His current whereabouts are unknown.