Knuckle Bine is an Unidentified Beast Hunter and the apprentice of Morel Mackernasey in Hunter x Hunter. He first appears during the Chimera Ant arc as a member of the team assembled to eradicate the ants. Despite his intimidating, delinquent appearance—characterized by a pompadour hairstyle and a muscular build often hidden under a white overcoat—Knuckle is profoundly compassionate and emotionally sensitive. He frequently becomes moved to tears, cares deeply for others, and has a habit of taking care of abandoned animals. This stark contrast between his rough exterior and his gentle heart defines his character. Knuckle is hot-headed and can be impulsive, but he also demonstrates strong strategic thinking and can adapt to cooperate with Hunters of very different abilities and temperaments.

His motivations are rooted in a sense of duty and protection rather than personal ambition. As a licensed Hunter, he uses his skills to confront dangerous threats, and during the Chimera Ant crisis he commits fully to the mission, even when it puts him at great personal risk. In the story, Knuckle plays a critical supporting role. He teams up with his close friend Shoot McMahon and their mentor Morel to face the powerful Chimera Ants, specifically engaging the Royal Guard Youpi. His tactical contributions are as important as his combat ability, and his emotional maturity gradually influences those around him. His most significant development occurs through his interactions with the ants and with Gon Freecss. Knuckle’s empathy allows him to see the humanity in his enemies, but he also struggles with the harsh realities of battle, showing that his softness does not equate to weakness.

Knuckle’s Nen abilities center on aura management and are built around concepts of debt and repayment. He can accurately gauge an opponent’s total aura and consumption rate. His primary technique is a Conjuration and Manipulation ability that creates a dwelling named APR (Absolute Permission Royalty), which attaches to an opponent and tracks a loan of aura. When Knuckle punches an opponent without using Ten, he lends them aura, increasing their debt. The interest on the debt grows over time. The opponent can reduce the debt by inflicting damage on Knuckle, but if the debt surpasses a certain threshold or if a set time limit expires, the target is forced into a state of Zetsu for a period equal to the number of days the interest accrued. This ability demands careful calculation and patience, as Knuckle must survive long enough for the loan to mature. He also uses a physical fighting style complemented by his Nen, and his resilience allows him to withstand attacks from far stronger opponents. His unique combination of combat skill, emotional depth, and inventive Nen makes him one of the most memorable allies in the later part of the series.