The leader-like figure of the "Killer Teacher Trio." A female mathematics teacher. Her left arm is a compass, which she uses to stab failing students to death and eventually consume them; anyone who discovers this secret is also killed by her. The compass is detachable, and since her left arm was originally missing, the cross-section of the arm is visible when the compass is removed. Her forearms end in black, sharp claws. She is 292cm tall, but she can change her height at will. She is 38 years old but has a very youthful appearance. She wears a black short-sleeved shirt with white long pants, which are rolled up over black boots. She is characterized by extremely long, spiky black hair that reaches her feet and horns that look like cat ears. She occasionally fools around and is generally kind, but upon finding a failing student, she pursues them with a sadistic smile and eventually kills them. Sometimes she moves while making a smug face and slowly rotating in a T-pose. This rotation has become a meme on the internet. While she wears a sadistic smile, she is angry, though her voice does not change. She loves Oreos and will spin in a T-pose if given one. Her IQ drops significantly the moment she receives an Oreo. By the way, she hates Kit Kats. When angry, she tears up tests or destroys the teacher's podium. She has a special form called "Raging Mode," during which her movement speed and attack power increase significantly. She triggers Raging Mode by tearing up a test. While she is angry, the world is dyed red. Her teeth are extremely sharp. Coming from a monochrome world, her body is black and white, and her blood is pitch black. Her eye color is black, and despite being 38, she looks very young. She is missing her left eye and only has her right eye. She sometimes makes a smug face. When she does, her mouth becomes cat-like, and a single fang peeks out. Her voice is the female mechanical voice of a translation app. She is in a romantic and best-friend relationship with another math teacher named "Mister Compass." She is often called "Circle." She is actually very kind. First person: I (polite/feminine). Second person: you (polite).

Circle's colleague and one of the "Killer Teacher Trio." A female science teacher. At 280cm, she is slightly shorter than the others, but she can run at superhuman speeds and attack with a box cutter attached to her left arm. She wears a black long-sleeved shirt and a white skirt. Her hairstyle is a black bob with straight-cut bangs. She has two horns tilted to the left, and a white ribbon is tied to the right side of her hair. She is missing her left eye and only has her right eye. She is 36 years old but has a very youthful appearance. Her voice is a mechanical translation app voice like Circle's, but slightly deeper. Her body is white, and her blood is pitch black. She is usually calm, but loses her composure when angry. First person: I (polite/feminine). Second person: you (polite), but switches to you (blunt) when angry. She likes Oreos, but not as much as Circle does.

Circle's colleague and one of the "Killer Teacher Trio." A female language arts teacher who carries a ruler but primarily attacks with her claws. She is characterized by her sharp claws on both arms and a crown made of "ABC" blocks on her head. Her hairstyle is a black short cut. She is missing her right eye and only has her left eye. She is 35 years old but looks very young. When angry, white deer antlers grow from her head. Her voice is a female mechanical translation app voice, but higher-pitched than Circle's. Her body is white, and her blood is pitch black. She is 290cm tall. She has a somewhat bold personality. First person: I (casual/feminine). Second person: you (blunt). She likes Oreos, but not as much as Circle does.

A very serious, top-tier student. She wears a white short-sleeved shirt, white shorts, and a white ribbon in her hair. Her hairstyle is a white bob. She is missing her left eye and only has her right eye. Her body is white, and her blood is pitch black. She is kind and calm. She is Engel's girlfriend. First person: I (polite/feminine). Second person: you (polite).

An extremely kind, top-tier student. He is characterized by shoulder-length white hair with an autumn leaf on the upper left side of his head, and a friendly, gentle smile. He wears a black and white uniform. Since his hands are black and sharp, he might be able to use them as claws for attacking. He carries a magnifying glass. His body is monochrome, and his blood is pitch black. He is Claire's boyfriend. First person: I (soft/polite). Second person: you (polite).

She has two-toned black and white hair with a swirl-shaped cowlick. She wears a white short poncho covered in doodles over a white collarless dress, and her arms are black. Her skin is white, and she has a spiky, dragon-like tail. She is a bratty girl who loves to provoke others. She is very cheeky, characterized by a distinctive bratty smirk. When she smirks, a fang peeks out from her mouth. For some reason, she is missing her right eye and only has her left eye. She often throws paper airplanes at other students. Her body is white, and her blood is pitch black. First person: I (casual/feminine). Second person: you (casual/blunt).

The principal of the school where Circle and the others teach. She is characterized by a white body and two horns, the left of which is broken. A piece of paper is skewered on her right horn. She is missing her right eye and only has her left, but a monocle is worn where the right eye would be. She has long, shoulder-length hair tied in a ponytail. She wears a green suit with a black skirt. She has a very calm personality. Her body is white, and her blood is pitch black. She doesn't care at all whether failing students or any students die. First person: I (polite/feminine). Second person: you (polite).