Jyugo, inmate number 15, is held in building thirteen, cell thirteen of Nanba Prison, where he was sent after being arrested on charges of larceny. He is a remarkably talented escape artist who successfully broke out of every correctional facility he was sent to before arriving at Nanba, a record that defines much of his identity. His physical appearance includes wavy black hair with red bangs, lightly tanned skin, and unique eyes that are not only two different colors from each other but are known to change color regularly, turning red when he uses a particular power. He wears silver hoop earrings, his nails are painted black, and his identification number is tattooed on his right cheek. His body is also marked with numerous other tattoos, likely identification numbers from previous prisons, along with barcode tattoos and various scars, including large spiky ones near his joints and many across his back. He is always barefoot and wears a torn black-and-white striped inmate jumpsuit to accommodate the thick, black shackles around his neck, wrists, and ankles, which can transform his limbs into large, powerful blades when activated.

Jyugo possesses a confident and impulsive personality but is also defined by a deep and pervasive apathy. He becomes bored very easily and his primary, and seemingly only, genuine talent is jailbreaking. He has received no basic education, leaving him unable to read, write, count, or swim, and he has poor stamina and physical abilities. The constant belittling he receives from his friends regarding his lack of general skills has taken a toll on his self-esteem. Despite his flaws, he is a deeply compassionate and selfless person, having done things for each of his cellmates that significantly changed their lives for the better, even if he himself does not remember these acts clearly and fails to understand why they hold him in such high regard. The core of his character is a profound emptiness. He has no concept of greed or motivation and admits to never having enjoyed or wanted anything, envying the perpetual excitement and drive of his friends, from whom he derives his only happiness. Described by a guard as empty, he struggles with feeling selfish for even wishing for his friends safety and happiness. He tends to blame himself for everything, struggles to open up to others, and prefers to shoulder his burdens alone, though the presence of his friends is typically enough to relieve his anxieties.

Jyugos primary motivation is to find the mysterious guard with a scar on his neck. In one prison, Jyugo awoke to find his shackles already placed on him, and he assumes the scarred guard was responsible. Believing the shackles make him a monster and unable to remove them himself, he has vowed to find this guard. He has been used as a human experiment by the man with the scar, where his blade abilities were presumably manufactured, but he has no memories of this incident. He managed to escape that organization with the help of an unknown guard who died in the process. He constantly escapes from prisons not necessarily to gain freedom, but to extend his sentence and continue his search, having determined that Nanba Prison might be the final place where he can find the scarred man. Another underlying motivation develops as he begins to wish to prove his worth and start over alongside his friends.

In the story, Jyugo is the central figure around which the main cast revolves. He is the one who, at various points in the past, met and saved his three cellmates, Uno, Nico, and Rock, before they all eventually reunited in Las Vegas and were later transferred to Nanba Prison. Of his cellmates, he is closest to Uno, with whom he shares a longer history and a deep bond of trust. Nico looks up to him like an older brother, and Rock listens to his plans. His relationship with the guard Hajime Sugoroku is particularly significant; Hajime trusts him the least and keeps the closest watch on him, often being the target of Jyugos teasing through escape attempts. However, Hajime is also the one who directly confronts Jyugo about his emotional emptiness and later gives him a chance to start over. Jyugo also has a violent past with another inmate, Musashi, with whom he was once cellmates. When they discovered each others superhuman powers, Musashi mistook Jyugo for an enemy and attacked, leading to Jyugo retaliating with his blades and slicing out Musashis only remaining eye. He is also the son of a notorious prisoner, Inmate 610, known as the Eternal Fugitive and the only person to have ever escaped Nanba Prison before.

Throughout the narrative, Jyugo undergoes significant development. Initially presented as purely apathetic and driven by an almost mechanical need to escape, he begins to confront his own internal void after a violent episode where he loses control of his blade powers and is subsequently imprisoned in an underground cell. In conversation with Hajime, he acknowledges his lack of desires and his habit of running away from his true feelings. He eventually realizes that he must be greedy and stop running, asking for a chance to start again. He vows to face everything directly, including the mystery of the scarred man and his shackles, and to find his own purpose rather than simply living vicariously through the passions of his friends.

Jyugos notable abilities are highly specific. He is an unparalleled genius at opening any kind of lock, whether mechanical or electronic, making him an exceptional escape artist. His primary weapon is the strange power of the black shackles he wears; when activated, they transform his limbs into enormous, powerful blades. However, using this ability seems to cause him to lose control, entering a rage-filled state where he attacks indiscriminately and his eyes turn completely red. Apart from these talents, his other abilities are miserably poor, and he is often caught quickly during escape attempts when relying on his own physical capabilities alone.