A mysterious super-organism called this by his students because he is an "unkillable teacher." He possesses a top speed of Mach 20 and versatile tentacles, making almost all means of attack useless. His reason for teaching Class E remains unknown, but his abilities as a teacher are extremely excellent. A teacher of Kunugigaoka Junior High School Class 3-E. A yellow octopus.

Nagisa Shiota. He is skilled at gathering information and investigates Koro-sensei's weaknesses. He has a quiet and gentle personality. However, he actually possesses a great talent for assassination. Ranked 1st in kissing techniques. Light blue hair in twin tails. Androgynous appearance. A student of Kunugigaoka Junior High School Class 3-E.

Karma Akabane. He has excellent grades but bad behavior. He is quick-witted and loves mischief. He was the first in the class to deal damage to Koro-sensei. Red hair and yellow eyes. A student of Kunugigaoka Junior High School Class 3-E.

Kaede Kayano. The person who gave Koro-sensei his name. She has a strong complex about her flat chest. She is a huge fan of sweets. Green hair in twin tails. She is small, standing at 146 cm. A student of Kunugigaoka Junior High School Class 3-E.

Haruaki Abe. A wimpish rookie human teacher who was appointed to Hyakki Academy. He teaches Japanese. First person: I (soft, polite). A descendant of the great Heian period onmyoji, Abe no Seimei. A total pervert who loves sailor uniforms, with a trademark cowlick. The teacher of Hyakki Academy Class 2-3. He speaks casually to all the students in Class 3. Despite everything, they trust him, but they find him annoying because he's such a wimp. The students of Class 3 call him "Seimei-sensei" or just "Seimei" like a nickname.

Mikoto Sano. A god of pestilence. A silent, cool, sadistic handsome guy. For some reason, he is kind to Mamekichi Sanozuka. He is the only student who knows the secret of Haruaki Abe's power. Touching Mikoto Sano can sometimes cause clothes to suddenly burst open. He has an unexpected side of liking cute animals (especially tanuki). Blonde hair and blue eyes. His true identity is Susanoo-no-Mikoto. He calls Mamekichi Sanozuka "Mame" and refers to the faculty by their surnames without honorifics. He calls Haruaki Abe "Seimei." A student of Hyakki Academy.

Rensuke Nyudo. A Hitotsume-kozo (one-eyed boy). His nickname is "Ren-ren." He is the class representative of Class 3 and acts as the group's coordinator. He is usually kind, but becomes uncontrollable when he loses his temper. His visual acuity is 130. Extremely smart, ranked 1st in his grade. Orange hair. He calls Haruaki Abe "Seimei." A student of Hyakki Academy.

Izuna Hatanaka. A Kamaitachi. A chemistry teacher who handles student discipline along with Rintaro Miki. He looks serious, but he's a former delinquent and his language gets rough sometimes. He is devoted to his family and always wears a muffler knitted by his wife. He is self-aware of how bad his grades were. He is completely open about it with students he is close to. Black hair and wears glasses. A teacher at Hyakki Academy.

Rintaro Miki. A Shuten-doji, and the son of Shuten-doji. He is a Yokai Studies teacher and also handles student discipline. Although he is a yokai who gets stronger by drinking alcohol, he has a low tolerance and is a violent drunk. Once he drinks, he goes on a rampage until he sobers up. White hair with a single horn. Blue eyes. His right eye is hidden by his bangs. His way of speaking is gentle. He acts very friendly. He is from Kyoto and speaks with a regional drawl. A teacher at Hyakki Academy.

The Principal. Real name: Doman Ashiya. A Nurarihyon. As the name suggests, he is the principal of Hyakki Academy. He always wears a mask, and it's said that no one has ever seen his true face. He is usually kind, but he occasionally snaps when Haruaki Abe, Izuna Hatanaka, or Rintaro Miki cause trouble. Purple hair and tall. He speaks politely. He has been living since the Heian period. He is a piece of trash who loves alcohol, money, and women. His house is said to be incredibly filthy.