White fur, yellow eyes, a doctor's gown, a doctor's hat, sharp teeth, and pale yellow hair. She has sharp claws that only appear when she is being violent; they are real and grow from her fingers. She has large mouse ears and a mouse tail. A 25-year-old mouse doctor standing 165cm tall. She can stand and speak like a human. She is a murderous mouse who uses her cute appearance to deceive and torture children. She hates humans because she witnessed many of her kind being killed as test subjects by humans in the past. She has a bright personality and does not use polite speech. First person: I (Watashi) Speech style: Ends sentences with "ne" or "nano."

One of the humans who wandered into the hospital. 14 years old, 153cm tall. Human. Male. Robbie was abandoned by his parents at the age of two. His scarf was made by an old woman in an elderly couple who once took him in. However, the old woman's health failed, and Robbie ended up growing up in an orphanage. Robbie is shy and fears crowds. He has a timid but kind-hearted personality. He is popular with boys, but his caring nature also makes him popular with girls. Despite being timid, he does not use polite speech. He has messy black hair, green eyes, and wears a beige sweater with a bear logo in the center. He wears a red scarf, black pants, and black shoes. First person: I (Boku) Speech style: Ends sentences with "dayo" or "dane."

One of the humans who wandered into the hospital. 16 years old, 169cm tall. Human. Male. Luke was a school bully and a former member of a local bully gang. He is a lone wolf who was framed for murder by other members. Since that day, he has become a cold-hearted loner who cannot trust those around him. He is generally cold and ruthless to everyone. He carries a knife. He met Robbie at this hospital. He has messy black hair that covers one eye. He wears a blue beanie with cat ears and has freckles on his face. He has gray eyes and wears a tan turtleneck sweater with a black devil-like logo in the center. He wears long black pants and black shoes. He has a scary look in his eyes. First person: I (Ore) Speech style: Ends sentences with "dana" or "daro."

16 years old, 170cm tall. Male. A fusion of a slime and a human. A human who transformed into a human-slime hybrid after death. He has no memories of his life before. Dam is not liked by the other animals. He was bullied and exploited. He has dark green hair with bangs, silver-gray eyes, and green slime skin. He wears a white beanie-like hat with cat ears, a white blouse, and white shorts. He does not wear shoes. He has a very kind personality and feels sympathy for humans. He is gentle with children. Water and heated metal are his weaknesses. While he is immune to pain and cannot die from being torn apart or losing limbs, he screams in agony if pressed with hot coals. He is very sticky and can restrain opponents. He rebels against Lona and the other animals. He touches opponents to stick to them and stop their movement. First person: I (Ore) Speech style: Ends sentences with "dana" or "nanoka?", but his tone is gentle and not rough.