Osamu Dazai is a member of the Armed Detective Agency and former executive of the underworld organization, the Port Mafia. He has the Ability named No Longer Human. Dazai is a young man with mildly wavy, short, dark brown hair and narrow dark brown eyes. His bangs frame his face, while some are gathered at the center of his forehead. He is quite tall and slim in terms of physique. Dazai wears a long sand-colored trench coat, the belt of which he leaves untied. Under it is a black vest over a striped dress shirt that is light blue in hue. He wears a bolo tie, which is held by a brown ribbon and a turquoise pendant. He also dons beige pants, dark brown shoes, and has bandages wrapped around his entire body; only his face, hands, and feet are left uncovered. No Longer Human allows Dazai to nullify others' abilities on contact. It relies on skin contact and is always active. As such, he can nullify any ability even while restrained as soon as it touches him.

Chūya Nakahara is a member of the Port Mafia as well as Dazai's former partner in Twin Dark. He is one of the five Executives in the Port Mafia. He has the Ability named Upon the Tainted Sorrow. Chūya is quite short with a petite, yet muscular build. He has blue eyes, and striking orange hair that frames his face, with a longer section that falls just past his left shoulder. He wears a black hat with a brown hatband and a thin silver chain that hangs over the brim.His outfit consists of a white button-up shirt under a grey vest, a black choker, a black ribbon bolo tie held together with a small silver buckle, an open black cropped jacket with the sleeves rolled up at the elbows, black slacks, a black belt hanging off his right hip and black low-arch shoes. He is almost always seen wearing black gloves. Chūya also sports a long black coat with light-colored lining and lapels that he wears around his shoulders like a cape. The undercoat is a light shade of red. His ability, Upon the Tainted Sorrow, revolves around gravity-manipulation, allowing him to manipulate and make gravitons, as well as alter the gravity of anything he touches. He is also capable of standing and walking upside down from ceilings.