Jyango, also known as Jango, is a character who first appears as an antagonist but undergoes a significant life change, eventually becoming a member of the Marines. He was originally the first mate, and for a time the captain, of the Black Cat Pirates, a crew from the East Blue. Before his life as a pirate, Jyango was a wandering dancer struggling to gain recognition. During a period of extended sleep, a peculiar striped mushroom grew on his chin. Driven by hunger, he ate the cap of the mushroom, which, despite its terrible taste, granted him the power of hypnosis.

His personality is flamboyant and somewhat bumbling. He has a deep-seated love for dancing, often incorporating moves like the moonwalk into his everyday walk. This passion for dance can even override his sense of self-preservation, as he once recklessly entered a dance contest while fleeing from the Marines. He is generally carefree but was known to be wary of his former captain's violent tendencies. Despite this, he remained loyal to Kuro's plans.

In terms of motivations and role in the story, Jyango's primary role during the Syrup Village arc is as the secondary antagonist. He aids his former captain, Kuro, in a three-year plot to eliminate a wealthy young woman named Kaya and inherit her fortune. His hypnosis is crucial to Kuro's schemes; he uses it to manipulate memories, put enemies to sleep, and even force Kaya to rewrite her will. However, his plan is thwarted by Usopp, who defeats him with a single explosive star.

After being abandoned by his crew, Jyango's path takes a dramatic turn in a cover story serialized in the manga, titled Jango's Dance Paradise. While fleeing the Usopp Pirates, he arrives at Mirrorball Island, where he disguises himself and wins a dance competition. There, he befriends the Marine officer Fullbody, who does not recognize him. When pirates attack the island, Jyango initially flees but ultimately returns to help Fullbody save a hostage. After his identity is revealed, he is captured and sentenced to death. Fullbody, moved by their friendship, performs a passionate dance in the courtroom to plead for Jyango's life. This leads to Jyango's acquittal, and he decides to hypnotize Fullbody into forgetting their friendship. However, before he can, both men see the beautiful Marine Captain Hina and are so captivated that they abandon the idea and enlist in her unit together as low-ranking soldiers.

Key relationships define his development. His friendship with Fullbody becomes the cornerstone of his new life, and the two are often seen dancing or acting in sync. He also harbors a persistent but unrequited romantic admiration for his commanding officer, Hina. His former loyalty to Kuro and his enmity with Usopp remain fixtures of his past. His development is central to his character, as he transitions from a wanted pirate to a dedicated, if eccentric, officer of the law. By the events of the Summit War of Marineford, he has risen to the rank of lieutenant commander. Years later, he is seen as a member of the World Conference security detail, demonstrating his continued service and integration into the Navy.

His notable abilities center on his unique hypnosis. To perform it, he swings a chakram-like pendulum attached to his heart-shaped glasses and chants the phrase "One, Two, Jyango". This can be used to put people to sleep, unlock hidden reserves of strength in allies, or implant commands. A critical flaw of his power is that he must cover his own eyes, usually by lowering his hat, at the last second to avoid hypnotizing himself; if he forgets, he becomes a victim of his own spell. Beyond hypnosis, he is a decently athletic fighter who uses the sharp pendulum as a projectile or melee weapon and incorporates exaggerated kicks resembling dance moves into his combat style.