Jinpachi Nezu is the captain of a pirate band that controls Lake Biwa. He is recruited to become the tenth and final member of the Sanada Ten Braves, taking on the role of the thunder warrior. He is a dark-skinned man with brown eyes and black hair, which he typically wears in a ponytail or dreadlocks, often adorned with feathers or hair tubes; his bangs cover one side of his face, revealing only one eye at a time. He is frequently seen wearing a large coat, fur, and has a goatee, stubble, and multiple necklaces as part of his distinctive appearance. He is also almost always accompanied by his loyal pet and companion, a black panther named Veronica.

Jinpachi possesses a free-spirited, hedonistic, and easygoing personality, with a strong aversion to being tied down or constrained. Above most things, he loves sake, women, and his ship. He is straightforward and openly expresses his admiration for women, though he can be superficial, as shown when he rejects the young priestess Isanami due to her small chest. Beneath this lighthearted and self-indulgent exterior lies a perceptive and surprisingly merciful individual. Rather than showing anger or holding a grudge against an enemy, he is more likely to become curious and enthusiastic about learning their nature, showcasing a unique attitude toward combat and conflict.

As the pirate leader of Lake Biwa, Jinpachi holds considerable influence and commands a large ship. He has an existing friendship with Juzo Kakei, which is strong enough that the two have sworn an oath of brotherhood. It is at Juzo's request that Jinpachi first appears, rescuing Saizo Kirigakure and the others from a perilous situation by bringing them aboard his vessel. His initial loyalty is not to the warlord Yukimura Sanada but to his sworn brother. However, after a brief conversation with Yukimura, he begins to warm to the young lord, even covering him with his own jacket against the cold. He is later motivated to travel to Ueda and formally join Yukimura's cause based on Juzo's teasing promise of a gorgeous, buxom blonde among the Braves, who turns out to be the ice-wielder, Anastasia.

Jinpachi is a formidable combatant whose primary and most notable ability is the manipulation of lightning and electricity, which grants him the epithet of the thunder warrior. He can summon powerful lightning bolts to strike down his enemies from a distance with devastating effect. In addition to this elemental power, he possesses incredible physical strength, showcased on one occasion when he effortlessly blocked a heavy blow from the massive warrior Miyoshi Seikai Nyudo using only one hand before defeating him with a lightning attack. He can also use his lightning powers defensively, such as generating an electric current to break free from being frozen solid.

His most significant moment of development and key relationship occurs with the spy Anastasia. When she reveals herself as a traitor and attacks him, Jinpachi is not angry or vengeful but rather curious and interested in truly understanding her. During their fight, he perceives her cold, icy facade as a cover for a deeply confused woman, a notion she vehemently rejects. After he defeats her by electrocuting her into unconsciousness, he spares her life, unlike how the other Braves typically deal with their enemies. When she later awakens in distress over her betrayal and the fact that she had been fighting for a fake heirloom, Jinpachi offers her a new path forward. He suggests she abandon her old life and embrace a free-spirited lifestyle like his own. She accepts his offer, and the two become traveling partners, choosing to observe Ueda Castle from a distance rather than officially rejoin the Braves, indicating a character arc that prioritizes personal freedom and connection over strict allegiance to a lord.