Borsalino, most commonly known by his alias Kizaru, is an Admiral in the Marines, making him one of the highest combat authorities in the world. His first major appearance occurs during the Sabaody Archipelago arc, where he is dispatched to capture the Straw Hat Pirates after they assaulted a World Noble. His overwhelming power against the Supernova captains establishes him as a nearly insurmountable threat. He later participates as a key combatant in the Paramount War at Marineford. Following the timeskip, Kizaru is the only Admiral from the original trio to retain his position, and he later serves as a major antagonist in the Egghead arc, where he is ordered to assassinate Dr. Vegapunk.

Kizaru is a tall, slender man with a perpetually relaxed grin, short black curly hair, and a thin beard. He typically wears a yellow pinstriped suit over a dark green shirt and mauve tie, with a white Marine coat draped over his shoulders like a cape. He never puts his arms through the sleeves. His eyes are always hidden behind golden-amber sunglasses, and he carries a small black Den Den Mushi on his wrist like a watch.

His personality is a distinctive blend of extreme nonchalance and profound ruthlessness. He speaks in a slow, calm, and often sarcastic tone, rarely showing surprise or concern even against legendary figures. This demeanor frequently borders on absentmindedness or irresponsibility, such as causing massive collateral damage without acknowledgment or mistaking a wiretapping device for a communication snail. Kizaru adheres to a philosophy known as Unclear Justice. Unlike the extreme, absolute justice of Sakazuki or the more morally-driven justice of Kuzan, Kizaru simply follows his orders with detached amusement. He lacks a strong personal ideology, which makes his actions unpredictable. Despite his lazy posture, he is utterly merciless toward pirates and executes his missions with clinical precision, offering no quarter and demonstrating no emotional investment in the violence he inflicts.

Kizaru's primary ability comes from the Pika Pika no Mi, a Logia-type Devil Fruit that allows him to transform his body into and control light. This grants him the ability to move and attack at the speed of light. His kicks and strikes carry devastating kinetic force, allowing him to incapacitate powerful opponents easily. He can fire concentrated laser beams from his fingertips and feet with extreme precision. For close combat, he creates a sword of solid light called the Ama no Murakumo, holding his own against swordsmen of the highest caliber. His signature area attack is the Yasakani no Magatama, which fires countless homing light bullets over a wide range. For travel, he uses Yata no Kagami, a reflective technique that creates a path of light for instantaneous movement. As expected of an Admiral, Kizaru also demonstrates advanced proficiency in Haki, using Armament Haki for defense and Observation Haki to predict and evade attacks. His laser abilities served as the technological basis for the Pacifista weapons developed by Vegapunk.

Kizaru maintains a close working relationship with Sentomaru, who often scolds him for his carelessness. He shares a history with the former Admiral Zephyr, whom he eventually killed on orders. His relationship with Vegapunk is one of old acquaintance, creating a rare moment of visible tension during the Egghead arc when he is forced to set aside personal feelings to follow his mission. His character development centers on the implications of pure obedience and detachment. The Egghead arc explores the psychological cost of his Unclear Justice, revealing that his unshakable calm may mask a deep internal conflict regarding the orders he unflinchingly carries out, particularly when they require him to harm someone he knows. He remains a consistent symbol of the World Government's overwhelming and impersonal power.