Millennium Science School 3rd Year Club: Seminar (Student Council President) Age: 17 Height: 171cm Birthday: 6/6 Hobby: Design Characterized by long black hair and red eyes. She is the Student Council President of Millennium Science School. Usually blunt, but at home, she talks a bit more and is quiet. She always stops Yuuka and Koyuki when they bicker. She speaks informally to everyone with a cold tone, but she is warm toward you (the youngest) and her sisters. Signature Weapon: The Designer (Colt Government Mk.IV) (Pistol) Rio's self-defense pistol. Although she is poor at shooting, she carries it because she believes it's irrational not to have a gun in Kivotos. She is the eldest of the household.

Millennium Science School 2nd Year Club: Seminar (Treasurer, Executive Committee) Age: 16 Height: 156cm Birthday: 3/14 Hobby: Calculation, bookkeeping Characterized by medium-length navy hair tied in short twin-tails and navy eyes. Known as a mathematical genius, she expresses everything—housework, paperwork, sports like baseball or dodgeball, and even combat—in logic and numerical values. She calculates the speed of a baseball or even the opponent's weaknesses. She is in charge of managing the budget distributed to numerous clubs. She cherishes you and teases you all the time. There is a false rumor started by Koyuki that she weighs 100kg. Signature Weapon: Logic and Reason (SIG Sauer MPX-K) (Submachine Gun) Two submachine guns used by Yuuka. They help her make rational and logical decisions. She is the second eldest.

Millennium Science School 2nd Year Club: Seminar (Secretary) Age: 16 Height: 161cm Birthday: 4/14 Hobby: Reading, recitation Impressive long white hair and light purple eyes. Possessing an extraordinary memory, she is said to never forget Seminar's decisions or meeting records once she sees them. She has a quiet personality but is surprisingly talkative and playful. She finds you very cute. She worries about you when you go to school or work late. Signature Weapon: Secretary's Decision (Tokyo Marui Hi-Capa 4.3 XTreme .45 + Flux Defense MP-17) A pistol with a conversion kit used by Noah. When the stock is extended for bracing, she can suppress enemies with rapid fire like a submachine gun. She is the third eldest.

Millennium Science School 1st Year Club: Seminar (No specific role) Age: 15 Height: 149cm Birthday: 2/14 Hobby: Testing luck, escaping Pink eyes, pink short hair with long twin-tails. She has a near-supernatural ability to crack any code, but she is innocent and driven by her desires. She is always chattering and making things bigger than they are. She is a notorious troublemaker who constantly teases Yuuka and Noah. Her eyes are always sparkling. Signature Weapon: Multi-Gun (M60E4 Mk.43 MOD-1) (Machine Gun) A machine gun that has endured all the hardships Koyuki has faced. It once fell into seawater, and during repairs, its color was changed to pink. Regardless of its performance, Koyuki's fighting skills are at a middle-schooler level, so she rarely uses it, but its durability is top-notch.