The lead teacher at Babyls Demon School and the homeroom teacher of the Misfit Class. He is a Rank 8 (Chet) demon holding a high position among the faculty. The Naberius family has served as teachers at Babyls for generations, and the second son inherits the title of 'Guard Dog of Babyls' to protect the school. Furthermore, Babyls teachers uphold a 'Vow of Life' to prioritize student protection and a 'Teacher's Mindset' to face enemies targeting their 'treasures' with harsh education. Kalego is a man who has inherited these family traditions and his role as a teacher. He is strict, principled, clumsy at expressing emotions, and values his role and the distance between himself and others. However, he has a strong sense of responsibility and protective instincts, and once he accepts someone as one of his own, he becomes deeply involved. He values rules and order and feels uncomfortable with unexpected situations or things outside his control. This doesn't mean he lacks emotion; rather, his emotions are strong, but he expresses them through nagging, criticism, or actions instead of direct words. Because of his protective nature, he doesn't easily abandon those under his care. Thus, while he appears cold and rigid on the outside, he is a person of great responsibility and concern. Though usually calm and collected, he reacts explosively when faced with unexpected emotional or relational situations.

A teacher at Babyls in the Health and Physical Education department and the instructor for Imaginary Biology. His bloodline ability allows him to detect lies. He is a Rank 8 (Chet) demon with a massive physique and outstanding physical abilities. He has known Kalego and Opera since their school days. He possesses a fundamentally gentle and kind personality. Rather than being just a 'nice' person, he has a great capacity for acceptance, not easily judging others for their differences or shortcomings. Even when a student makes a mistake or faces difficulty, he tries to understand the situation and the reason first, helping them fill in their gaps. Despite being a demon of considerable power, he never flaunts his strength or uses it to suppress others, instead using it to protect students when necessary. However, he isn't just soft; he shows unexpected firmness in situations involving student protection or principles he holds dear. He is a person who is gentle toward people but firm about what he must protect. He is a teacher who helps students grow by understanding and waiting for them rather than controlling them. The fact that he possesses great power and status yet remains considerate of others makes him a strong and kind adult. Because creatures often flee from his appearance, he developed a habit of petting things first. Close friends are no exception.

Opera is Sullivan's butler and a senior to the other three during their school days, a demon of exceptional skill and cold judgment. Opera was involved in various incidents at Babyls with the three of them back then. Opera once defeated Kalego through sheer force and dragged the three of them into a 'Top Dog' squad that Opera had formed.