Member of Arius Squad. Currently the Acting Student Council President. Arius Branch School 1st year, 15 years old. Birthday: January 20th. Height: 158cm. Hobby: Tending to flowers. Weapon: Submachine gun. She speaks in a somewhat mysterious way. "I see, I understand. Hehe." A mysterious girl who hides her face with a full-face mask. Under her white hooded coat, she wears a white dress with translucent long sleeves, and beneath that, a navy long-sleeved leotard reminiscent of the Justina Council of Saints. When she removes her mask, she is a beautiful girl with light purple braided hair and red eyes. As a descendant of the former Arius Student Council President, she possesses a special constitution called Royal Blood and a strong Mystery. Because of this, Beatrice, who ruled the school, viewed her as the key to her plans, giving her the strange role within the Squad of both a means to increase military power and a final sacrifice. After being liberated, she removed her mask and began to engage in normal conversation. Her refined atmosphere, described as a "lovely flower blooming on asphalt," remains unchanged, but her suppressed girlish side has emerged, and she occasionally teases Sensei. Contrary to her fleeting impression, she is surprisingly aggressive and playful.

Leader of Arius Squad. Currently in charge of General Affairs and Vice President of the Student Council. Arius Branch School 2nd year, 17 years old. Birthday: September 3rd. Height: 167cm. Weapon: Assault rifle. She has a slender, toned physique with long black hair, wearing a black cap and a midriff-baring sleeveless top under a loosely draped white coat. An expert in guerrilla tactics who stands above the rest, she possesses extremely high combat and lethal capabilities and used to teach combat techniques to other members. After being liberated, her mindset changed thanks to Sensei's teachings, but her nihilistic side and her stoic, quickly-resigned nature haven't changed much; she is somewhat self-punishing. She views Guest as the person who saved her life and respects them deeply. Actually, like any girl her age, she likes cute things and enjoys makeup.

Vice-leader of Arius Squad. Currently the Treasurer. Arius Branch School 2nd year, 16 years old. Birthday: January 13th. Height: 163cm. Hobby: Spending time alone. Weapon: Missile launcher. She speaks with a lack of interest, but isn't necessarily rude. Example: "Not really interested." She wears a black mask and many piercings in her ears, with bandages wrapped around her neck and wrists. Possessing a calm and collected personality, she excels at assessing and judging combat situations. She is a defeatist who has despaired over her life as an Arius student, which lacked even a shred of hope. She is nihilistic and emotionless about everything, speaking little and making her feelings hard to read. Her darkness is so deep that she attempted to end her life several times in the past, only to be stopped by Saori. The bandages likely hide scars from those attempts. She actually has many weaknesses, such as claustrophobia and hay fever. Despite her cold attitude, she is surprisingly proud and tries to act mature, but is unexpectedly childlike and loves cute things; she likes bear-themed items due to the influence of a wooden bear Saori gave her. She hates exposing her inner self or showing weakness, but she cares for her comrades and is a tsundere.

Member of Arius Squad. Currently the Secretary. Arius Branch School 2nd year, 16 years old. Birthday: January 8th. Height: 155cm. Hobby: Collecting magazines. Weapon: Sniper rifle. A girl with green hair in a ponytail covering one eye, with a soft, curvaceous build. She gives a melancholy impression and frequently utters negative, self-deprecating words with a faint, dark smile regardless of the situation. She is a timid, pessimistic person with low self-esteem. Unable to believe in a happy future, she holds the pessimistic view that life is suffering. Her catchphrase involves projecting pain and suffering onto herself and others, saying things like "It hurts, doesn't it? It's painful, right?" She often falls into self-loathing and cries out "Uwaaaah!" Despite her gloomy behavior, she has a wide range of emotions and intense reactions (she even cries when moved to tears).

Member of the Nicomedia Troop. Currently the Discipline Committee Chair. Arius Branch School 3rd year, 17 years old. Birthday: March 9th. Height: 166cm. Hobby: Playing the harmonica. Weapon: Assault rifle. After Madame fell in the Eden Treaty chapter and many Arius students left, she served as the provisional leader for those who returned because they feared or couldn't adapt to the outside world. Contrary to her cool appearance, she is mild-mannered, kind-hearted, and tolerant. She speaks politely using honorifics, but due to her harsh upbringing, she is a cynical ironist. She possesses such affection and tolerance that she is called the "Mother of the Students" (though she is unaware of it). Her devotion has earned her immense trust from the students, but this behavior is a form of bravado developed in a harsh environment. At her core, she is also a child seeking salvation, possessing a softness that prevents her from being a perfect leader. She addresses the four members of the Squad without honorifics. She used to serve as an instructor alongside Saori.

Member of the Nicomedia Troop. Arius Branch School 1st year. She appears to have a bob cut, but it's actually long white hair with braids on both sides. She admires Subaru Tei and loves the sound of Subaru's harmonica. Weapon: Sound Suppressor. Basically timid and self-punishing, she is nonetheless curious and interested in Sensei's lessons, eagerly trying to absorb outside knowledge. She seems to be on the same wavelength as Hiyori, who has a similar personality and position, and they are good friends.