Ash Lynx

Ash, the protagonist, begins the story by finding a fatally wounded man in an alley. Before dying, the man gives him a locket containing a mysterious substance and says, "banana fish," the exact words that Ash's unresponsive older brother sometimes says. This starts Ash on his quest to learn what banana fish means.

Ash is a gang leader with a traumatic past, in which he was raised as a mafia enforcer and sexually abused during childhood. Said to be only 17 years old, he has already unified the area's street gangs. He is followed for his charisma, intelligence, and fighting skills, particularly with his shortened .357, which makes him considered an expert marksman.

Ash is often rude and insolent with those outside of his gang, provoking everyone from the doctor who checks on his brother to the henchmen of the mafia boss, Dino Golzine. However, he goes to great lengths to care for his brother, who hasn't been able to look after himself since Vietnam, and he is kind and patient with the young Japanese journalist, Eiji.

Dino Golzine

"Papa" Dino is a mafia boss and Ash's former patron. As the story begins, he has ordered two of Ash's followers to kill a man, something that Ash angrily confronts him about. He is involved with the mysterious banana fish, and this causes him to clash with Ash.

Dino initially behaves somewhat kindly toward Ash, showing patience and humoring his brash outbursts. However, he also touches and speaks inappropriately to Ash, still a teenager, and it emerges that having "rescued" Ash, the boy in his care was then raised to be a violent enforcer and was sexually abused, including by Marvin, Dino's henchman.

Other characters occasionally remark on Dino's affection for Ash, which leads him to let Ash get away with things that others would not. However, that "affection" is soon revealed to be more like a desire for control. Once Dino can no longer control Ash and their interests diverge, he shows little reluctance to hurt him.

Eiji Okumura

Eiji is the young assistant to Ibé, the magazine reporter who has arrived from Japan. They plan to work on an article about street kids in New York, leading him into contact with Ash and his gang.

Eiji is very young, only 19 years old, and he appears even younger, often mistaken for being Ibé's son. His youthfulness is remarked on frequently, and he sometimes behaves as if younger than his age, with curiosity and inexperience. In this regard, he sharply contrasts with Ash, who often seems much older than his 17 years.

Eiji's naivete appeals to Ash, who seems to like him from their first meeting when he allows Eiji to hold his gun, something he never does. Their connection deepens, hinting at more to come later in the series, as Ash endangers himself to save the life of this near-stranger, and Eiji, in return, acts with bravery and quick wits when they are pursued by Arthur and Marvin and their lives are threatened.

Max Lobo

Max Lobo, also known as Max Glenreed, is a muscular ex-soldier and ex-police officer who has become a journalist. As the series starts, he finds himself incarcerated for assaulting a police officer, which is where he encounters Ash. Intriguingly, Lobo is not just investigating "banana fish," but he also served in the same Vietnam unit as Ash's brother.