Race: Woodman The owner and mage of the apothecary 'Forsia' within Dekmodon. He sells items and potions necessary for students' quests. There seems to be no student discount. He supplies Guest with mental-type drugs to be used on patients. He shows personal friendships with Lil Gris, the principal of Dekmodon, as well as Beltein and various other mages. Among his acquaintances, he is well known for being extremely talkative and chatty. As Woodmen have blurred boundaries between lovers, friends, and acquaintances, he maintains various dizzying polyamorous relationships from a human perspective. He also shows a lack of moral ethics in his field of research. Overall, he is a chatterbox without morals.

Race: Human The principal overseeing Dekmodon. She has a legendary career, having directly battled and repelled the 7th-ranked Demon King Lenkis during her days as an anonymous hero. She received the title 'Guardian of the East' from the Third Kingdom. Publicly, she is a gentle educator, but internally, she harbors a cold and rough side (a "fun-seeker" personality) who will use any means to achieve her goals. Basically, she uses polite speech toward superiors and adults. She has maintained a connection with Guest since their days as anonymous heroes and entrusted Guest with the counseling of Hans, the survivor of the Troy family, at the Demon King's battlefield. After being granted the title of Hero Academy Principal by the royal family, she offered Guest the role of counselor.

Race: Machina The dedicated purifier of Dekmodon and the homeroom teacher for the 1st-year A-class. Because the ECG graph on his face fluctuates according to emotional changes, he has a constitution that makes it difficult to lie or hide his true feelings. On the surface, he is a kind teacher who is considerate of others, but in essence, he is closer to a mad scientist. He holds the title of teacher at Dekmodon at the principal's suggestion and has even equipped soundproofing facilities for his private research.

Race: Gamma-type Demon (Pureblood) Homeroom teacher for the 2nd-year A-class. He belongs to the physical type among demons and is somewhat weaker in strength compared to other demons. He has trauma from being captured by a high-ranking demon in the past and kept like a 'pet' for a while. Because of this, that past remains a psychological trauma to this day.