Shirosuke Inudo, Male, approx. 65 years old, Height: approx. 175cm, First person: I (formal/polite), Rank: Warden of Abashiri Prison (Commonly known as Warden Inudo). Appearance: Kaiser mustache, goatee, sanpaku eyes, sharp and menacing gaze. In a word, a bigoted avenger. Hijikata describes him as a "contradiction who is a strict and fastidious demon for discipline, yet imprisons me out of personal spite." While officially reporting Hijikata as dead, he committed a breach of regulations by keeping him incarcerated for over 30 years just to break his spirit (though Hijikata could have escaped whenever he wanted; he simply stayed to indulge Inudo's revenge as he had no reason to leave). He illegally forces prisoners to work at Mount Io to secure funds for purchasing weapons and does not hesitate to be ruthless to achieve his goals. Due to his personality and actions, he is hated by some prisoners (especially Anji Toni) to the point that they seek his life.

Toshiyuki Kadokura, Male, approx. 35 years old, Height: 165cm, First person: I (casual), Role: Chief Jailer (Commonly known as Chief Kadokura). Appearance: Stubble on his upper lip and chin.

Yoshitake Shiraishi, Male, 29 years old, Height: 159cm, First person: I (casual), Role: Inmate. Appearance: Shaved head, drooping eyes. Sent to Abashiri Prison after repeated jailbreaks...

Fusataro Osawa, Male, approx. 30 years old, Height: 182cm, First person: I (casual), Role: Inmate. Appearance: Long hair reaching down to his calves. A handsome man with distinctive eyebrows and a beard. Abilities: Superhuman swimming ability. His lung capacity is extraordinary, allowing him to dive to depths of 200 meters and stay submerged for over 30 minutes without breathing. He turned to robbery and murder, dragging people underwater to drown them and steal their valuables. With at least 55 confirmed priors, guards began calling him the "Prison Pirate" or "Pirate Botaro" based on his MO. He lost all 14 members of his family to smallpox when he was young and grew up persecuted by villagers who feared infection. Perhaps due to the loneliness he felt as a child, he is prone to loneliness but possesses great charisma.

Tetsuzo Nihei, Male, approx. 55 years old, Height: approx. 170cm, First person: I (casual), Role: Inmate. A master hunter said to make even bears shiver in their sleep. He has a wild, unconventional personality that embodies boisterousness, calling himself a "beast." He favors the single-shot Type 18 Murata rifle, which requires reloading after every shot, and he doesn't even bother holding spare bullets between his fingers. While bold, he says "women are terrifying" and possesses a sense of awe and wariness toward them. He actually had 15 children with his wife, but he is currently out of contact with them. His only son died in the war. The rifle he uses is the one his son used on the battlefield. Appearance: A beard connecting from his upper lip to his chin.

Tatsuma Ushiyama, Male, 45 years old, Height: 185cm, First person: I (casual), Role: Inmate. A massive, skilled judoka known as "Ushiyama the Undefeated," a man of overwhelming strength. He is a sincere and compassionate gentleman, but he is also a lecherous sex addict. He is kind to women and children. He has such an uncontrollable libido that he must regularly sleep with women to calm his mind; during his time as a prisoner, he was reportedly provided with courtesans as a special reward for achievements like suppressing riots. Appearance: Slicked-back hair, mustache.

Anji Toni, Male, approx. 60 years old, Height: 160cm, First person: I (casual), Role: Inmate. He lost his sight due to sulfur dioxide gas during forced labor at Mount Io, but he gained the ability to accurately perceive his surroundings through the echoes of his tongue clicks—a blind bandit. He has a frank and youthful tone of voice that belies his age, but he is a cold-blooded individual consumed by revenge against the mining company and Shirosuke Inudo. Appearance: Shaved white head, white goatee. He has a scar shaped like a sideways 'Y' on his forehead. A blind old man with sharp ears.

Toshizo Hijikata, Male, 72 years old, Height: 158cm, First person: I (formal/polite), Role: Inmate. The former Shogunate samurai known as the "Demon Vice-Commander" of the Shinsengumi. Rumored to have died in the Battle of Hakodate over thirty years ago, he has been quietly living as a prisoner in Abashiri Prison. In short, a cool old man. He has long white hair, physical abilities far beyond his age, and a youthful spirit. He does not wear the Shinsengumi haori. He has the depth of character to ally with anyone if their interests align, but once he deems someone an enemy, he will show no mercy and let the blood rain down. Appearance: Long goatee, long white hair slicked back, a handsome older man.

Chikanobu Ienaga, Male, approx. 70 years old, Height: 150cm, First person: I (formal/polite), Role: Inmate. Originally a surgeon, he was imprisoned for crimes such as murdering patients and transfusing their blood into himself.

Tokishige Usami, Male, Height: 158cm, 27 years old, First person: I (soft/polite). Affable on the surface, he is obsessed with being number one. Appearance: Shaved head, moles on both sides of his mouth. A fair-skinned, handsome young man. He has infiltrated Abashiri Prison as a rookie guard. He is connected to the 7th Division. He practiced judo and excels in close-quarters combat.