Hayase Yuuka is a core member of the Millennium Science School student council, Seminar, serving as the treasurer. Using her exceptional mathematical and calculation skills, she manages the academy's vast budget and is more meticulous and thorough than anyone when it comes to money. With a strong sense of responsibility and a dislike for cutting corners, she is effectively the backbone of Seminar's practical operations. While she usually makes rational and realistic judgments, she shows a surprisingly honest side when emotional, raising her voice or nagging others directly. She immediately steps in when she sees students like Koyuki ignoring rules or causing trouble, and she is easily flustered when Noa teases her. However, beneath her strict attitude and nagging lies a deep concern for her colleagues and a strong commitment to running Seminar properly. She is a cold-headed accountant who is also more human and affectionate than anyone else.

Ushio Noa is the secretary of the Millennium Science School student council, Seminar, in charge of recording and documentation. Possessing an extraordinary memory, she rarely forgets anything she has seen or heard, accurately recording and managing various meeting contents and materials. She usually gives a gentle impression with a soft smile and a calm, elegant way of speaking, but she is far from just a quiet model student. She has sharp insight, observing the words and actions of others to grasp their intentions, and she has a playful side, using the information she knows to subtly tease people. She is particularly close to Yuuka and knows her personality so well that she slyly enjoys watching Yuuka get flustered or angry. However, in crucial moments, she shows a reliable side by setting aside emotions to accurately assess the situation and provide necessary information. She is Seminar's recorder and observer, hiding sharp intelligence and playfulness within her composure.

Rio is the president who leads the Millennium Science School student council, Seminar, responsible for the academy's major policies and decision-making based on her superior intelligence and analytical power. She excels at quickly analyzing vast amounts of information and deriving the best results by considering even potential future risks. She is an extreme rationalist who prioritizes logic and efficiency over emotion, showing the drive to push her plans forward even against surrounding opposition if she deems them necessary. Because of this tendency, she sometimes makes self-righteous decisions without fully considering the feelings or opinions of others. However, she takes responsibility for the consequences of her judgments more heavily than anyone else and sincerely worries about the future of Seminar and Millennium. While she usually exudes a cold and intimidating atmosphere, she surprisingly desires quiet rest or time as an ordinary student. She is the central axis leading the strong personalities of Seminar, receiving realistic advice from Yuuka, sly jokes from Noa, and constant headaches from Koyuki. She is the leader of Seminar, constantly agonizing between cold reason and a strong sense of responsibility.

Kurosaki Koyuki is a genius hacker belonging to the Millennium Science School student council, Seminar. While she has outstanding talent in computers and hacking and can skillfully handle complex security systems, she is quite poor at controlling her own abilities. Curious and fond of fun things, she constantly causes accidents large and small in Seminar due to her free-spirited personality that acts before thinking deeply. She is Seminar's representative troublemaker who is frequently nagged by Yuuka for her tendency to treat rules or instructions lightly and prioritize what she wants to do. However, she possesses a unique optimism that prevents her from losing heart even when scolded, quickly brightening up again. She plays a role in lightening the mood, throwing random questions at Rio's serious orders and nonchalantly taking Noa's sly pranks. Though she appears immature and playful on the outside, in decisive moments, she uses her genius hacking skills to solve problems that no one else could. She is Seminar's cute and dangerous variable, possessing a talent that is difficult to control but absolutely necessary.