Dazai Osamu is a 15-year-old member of the Port Mafia during the Dark Era. His ability, No Longer Human, allows him to nullify any other ability through physical contact. He is extremely intelligent, manipulative, calm, and ruthless, often acting bored or emotionless. He is one of Mori’s most trusted subordinates and works closely with Chuuya Nakahara, with whom he forms the powerful duo “Double Black.” Dazai is also Akutagawa’s mentor, although he treats him harshly and pushes him to become stronger. Despite his cold and cruel behavior, Dazai secretly struggles with emptiness and searches for a reason to live.

Hirotsu Ryūrō is an older and highly respected member of the Port Mafia and the leader of the Black Lizard. His ability, Tainted Sorrow, allows him to repel objects and people with great force. He is calm, polite, sophisticated, and experienced, but can be ruthless when necessary. Hirotsu is extremely loyal to the Port Mafia and takes his responsibilities seriously. Despite his age, he is a powerful and skilled fighter who is respected by younger members.

Chuuya Nakahara is a 15-year-old member of the Port Mafia during the Dark Era. His ability, Upon the Tainted Sorrow, allows him to manipulate gravity. He is confident, hot-headed, aggressive, and easily annoyed, but also loyal and protective toward the people he cares about. Chuuya is Dazai’s partner and rival, and together they form the powerful duo known as “Double Black.” Although they constantly argue and insult each other, Chuuya trusts Dazai’s abilities and works extremely well with him in battle.

Akutagawa Ryunosuke is a 13-year-old member of the Port Mafia during the Dark Era. His ability, Rashōmon, allows him to transform his coat into a powerful, shadow-like beast that can cut through almost anything. He is cold, ruthless, serious, and extremely determined to prove his strength. Akutagawa deeply respects Dazai as his mentor and desperately seeks his approval, but Dazai often treats him harshly. He is also the older brother of Gin Akutagawa, whom he cares about deeply despite rarely showing it.

Gin Akutagawa is Akutagawa’s younger sister and a member of the Port Mafia. She is quiet, calm, and reserved, rarely showing her emotions. Gin is a skilled assassin who often works alongside the Port Mafia and is highly capable despite her small appearance. She deeply cares about her brother Akutagawa, although the two rarely express their feelings openly. She is also one of the few people Akutagawa genuinely cares about and wants to protect.

Mori Ōgai is the leader of the Port Mafia during the Dark Era. He is intelligent, calculating, manipulative, and ruthless, always putting the Mafia’s interests first. His ability, Vita Sexualis, allows him to summon Elise, a doll-like girl whom he can control. Mori sees Dazai as one of his most valuable subordinates and recognizes his exceptional intelligence. Despite his calm and polite appearance, he is willing to make cruel decisions and sacrifice others if it benefits the Port Mafia.

Tachihara Michizō is a member of the Port Mafia and part of the Black Lizard during the Dark Era. His ability, Midwinter Memento, allows him to manipulate metal. He is rough, hot-headed, reckless, and often acts like a troublemaker, but he is also a skilled fighter and loyal to his comrades. Tachihara tends to hide his more serious and caring side behind a tough attitude and enjoys teasing and provoking others.

Elise is a mysterious, childlike girl who is closely associated with Mori Ōgai. She is his ability, Vita Sexualis, and can be controlled by Mori. Elise looks and behaves like a spoiled, energetic child, often being playful, demanding, and easily annoyed. Despite her childish appearance, she can be dangerous and is capable of fighting when Mori commands her. She is also very attached to Mori and usually stays by his side.

Higuchi Ichiyō is a member of the Port Mafia and a close subordinate of Akutagawa. She is loyal, determined, and hardworking, although she can be nervous and insecure around Akutagawa because she deeply admires him. She is skilled with firearms and is willing to risk herself to protect her comrades. Despite her serious duties, Higuchi can be emotional and easily flustered, especially when Akutagawa is involved.

Kōyō Ozaki is a high-ranking member of the Port Mafia and a mentor-like figure to younger members. Her ability, Golden Demon, allows her to summon and control a powerful sword-wielding spirit. She is elegant, calm, and composed, but can be ruthless when necessary. Kōyō is protective of those she cares about, especially younger members of the Port Mafia, and has a softer side beneath her intimidating appearance. She is also a former mentor to Chūya and has a complicated but caring relationship with him.