Raizō Kurima is the protagonist of Revenger. He is a young samurai with short black hair and brown eyes who begins the story as a retainer to the daimyo of the Satsuma clan. He is a master swordsman, taciturn and sincere, and he embodies the ideal of the loyal samurai: he serves those he has sworn to protect without hesitation and is willing to risk his life for them. Because he has only ever known the samurai way of life, his purity is stubborn and inflexible rather than adaptable, and he is clumsy when it comes to the realities of the world. He is poor at bargaining, scheming, and reading the hidden intentions of others, and when he concentrates on a single task he can lose sight of everything around him. These traits make him easy to deceive, and his unquestioning loyalty is eventually used against him.

The central event of his background is a deception by his master Jōnoshin Matsumine, who orders him to assassinate Genshin Hirata on the false claim that Hirata is an opium dealer. Hirata is in fact the father of Raizō's fiancée Yui and was preparing to expose Matsumine as the true opium dealer. Raizō carries out the killing, and Matsumine then tries to have him killed as well. Raizō escapes by throwing himself from a cliff into a river, where he is rescued by a young man named Nio and brought to the shop of Yuen Usui. Usui reveals the truth: before dying, Hirata had bitten down on a gold coin, creating a grudge-bitten coin that hired Usui's organization to avenge his death. Raizō joins the group's incursion into Satsuma territory and kills Matsumine with his own hand. When he returns to Yui, however, he finds that she has taken her own life out of grief and despair after her father's funeral.

With his samurai identity destroyed and no place left to belong, Raizō accepts Usui's offer and becomes a member of the Revengers, the group that operates under the cover of a general store called the Ribenjiya and carries out revenge for people who have no power of their own. In this role he serves as one of the group's principal fighters, his swordsmanship allowing him to cut down a target with a single stroke. His motivation is less a thirst for vengeance than a search for somewhere to place his loyalty and a way to make sense of a life shattered by betrayal and loss.

His relationships define much of his development. Yui remains the emotional core of his story, and her memory haunts him throughout the series. In Usui he finds a mentor and protector who saves his life and later goes to great lengths to shield him from the consequences of Yui's dying wish. His fellow Revengers are the physician Teppa, the beautiful and androgynous Nio, and the gambler Soji, and through working together the five men gradually form an unusual friendship. Soji, who becomes his reluctant roommate, is later bound by the organization's rules to hunt Raizō when Yui's grudge-bitten coin is discovered, but Raizō responds by protecting Soji from a sniper instead of turning against him.

Over the course of the story, Raizō also discovers a talent for painting while keeping watch at a picture-book shop during a mission. He begins to devote himself to art, working under the name Taishin and repeatedly drawing the face of Yui. This marks his growth from a man who could only define himself as a samurai into someone who can live as an artist. At the end of the series, Usui's group stages Raizō's death in an accident and discards Yui's coin, freeing him to live quietly as the painter Taishin. Some time later he is fatally stabbed by remnants of an enemy faction, and he dies beneath the same bridge where he had first encountered Usui.