"Banana Fish" is a 24-episode anime series adapted from Akimi Yoshida's manga of the same name. Set primarily in New York City during the 1980s, the story intertwines crime, conspiracy, and personal struggle. The narrative centers on Ash Lynx, a 17-year-old gang leader in New York, who was raised by the mafia boss Dino Golzine after being taken in as a child. Ash is intelligent, resourceful, and a skilled fighter, but his past is marred by abuse and manipulation under Golzine's control.

The plot is set into motion when Ash's older brother, Griffin, a Vietnam War veteran, becomes catatonic after uttering the words "Banana Fish." Investigating the meaning behind this phrase, Ash discovers it is linked to a mysterious drug being used to manipulate people into violent behavior. This drug is tied to a larger conspiracy involving Golzine, corrupt politicians, and powerful organizations. Ash's quest for the truth leads him to cross paths with Eiji Okumura, a Japanese photographer's assistant who becomes his closest confidant and emotional anchor. Their bond deepens as they navigate the dangerous underworld together.

Throughout the series, Ash confronts numerous adversaries, including rival gangs, corrupt law enforcement, and Golzine's associates, all of whom are entangled in the "Banana Fish" conspiracy. The story explores themes of loyalty, trauma, and the cost of power, as Ash struggles to protect those he cares about while seeking freedom from his past. Supporting characters, such as Shorter Wong, a loyal friend and fellow gang leader, and Max Lobo, a journalist investigating the conspiracy, play pivotal roles in the unfolding events.

The narrative is marked by intense action sequences, emotional depth, and a focus on the psychological toll of violence and exploitation. As Ash uncovers the truth about "Banana Fish," he must also grapple with his own identity and the choices he has made. The series concludes with a poignant resolution that underscores the enduring impact of Ash and Eiji's relationship, leaving a lasting impression on viewers.