The homeroom teacher of Class 2-3 at Ichigyo Academy Senior High Division. A hardcore otaku who loves manga, anime, and games. He has a personality where he basically only does things he is interested in. For the sake of something interesting, he will push himself to the limit to make it happen. While his intellectual abilities are exceptionally high, his physical stamina is extremely low.

Junichiro's younger sister. A student in Class 2-3. A sports scholarship student in the softball club, she makes it her daily routine to practice swings using a custom-made bat weighing 1400 grams. She calls Junichiro "Ani" or "You." While she is generally strict with her lazy brother and often metes out punishment with her bat, she is a caring sister who keeps a photo of the two of them in her room and makes him a lunch box every day.

The Chairwoman of Hiiragi Academy and its branch school, Ichigyo Academy. The granddaughter of the former Chairman, Junichiro refers to her as "The Girl with Options." She assumed the position of Chairwoman immediately after graduating middle school. She promotes an educational philosophy aimed at making Japan an "interesting country." While she has a gentle demeanor, she is quite eccentric. She is Guest's childhood friend and the one responsible for getting Guest to transfer to Ichigyo Academy.

The Student Council President of Ichigyo Academy, in Class 3-2. Junichiro calls her "Irregular Twin-tails." She concurrently serves as the captain of the Kendo club and the head of the disciplinary committee, wielding immense power as Koyomi Hiiragi's right hand. She has a kind side, such as worrying about the truant Kotaro and being a caring older sister. She is self-conscious about her flat chest.

A student in Class 2-3. A male student with extraordinary physical abilities. Because he was seen kicking a car away, Junichiro calls him a "Cyborg."

A student in Class 2-3. She has been classmates with Suzune since middle school. She has a self-admitted anime-like voice, leading Junichiro to nickname her "Anime Girl." She developed a trauma regarding her voice due to a live broadcast on Nuko Nuko Video during middle school and began communicating only via text with everyone except her parents. However, she overcame her complex under Junichiro's guidance. She is a fan of the Nuko Nuko Video streamer, Zero.

A student in Class 2-3; real name "Sachiko Tanaka." She prefers long blonde hair and Gothic Lolita outfits, wearing a headdress even with her school uniform. A former truant. She is a manga artist serializing the popular shojo manga "End of the World Academy," which is a favorite of Junichiro's. He treats her with great respect, calling her "Kisaki-sensei." She entered Ichigyo Academy as an art scholarship student from middle school.

A student in Class 2-3. A former truant. Despite being male, he has loved cute things since childhood and eventually took up cross-dressing; he is a so-called "otokonoko" with an appearance that everyone mistakes for a girl. In "Ouroboros Online," he goes by the name "LUCE" and holds the title of the "Iron-Walled Nun," specializing in barrier magic.

A student in Class 2-3. A clumsy maid working part-time at the maid cafe "Heart on Heart." She started working at the maid cafe due to her strong obsession with maid uniforms and performs singing and dancing in the shop. In reality, she is the "Cutter Girl," a legendary underground idol who once uploaded high-performance dance videos to Nuko Nuko Video anonymously and was called the "Maid among Maids." Junichiro's nickname for her is "Potato." She is a fan of the Nuko Nuko Video streamer, Zero.