Kanjuro, also known as "Evening Shower" Kanjuro, is a samurai from the Wano Country whose life is defined by a deep and tragic performance. He was born into a famous theater troupe, and as a member of the Kurozumi family, he witnessed his parents being killed on stage simply because of their heritage. This childhood trauma left him emotionally broken, causing him to forget how to live as himself. He found his only purpose in acting as someone else, and for the rest of his life, he sought a grand stage on which to die. He was eventually taken in by Kurozumi Orochi, who avenged his parents and gave him a role to play: that of a loyal retainer to the Kozuki Family.

As a retainer, Kanjuro appeared to be a caring, selfless, and slightly absent-minded individual. He showed great concern for his comrades, willingly sacrificing his own freedom so that Kin'emon could escape, and displayed bravery in battle. He often seemed overzealous, once offering to commit harakiri after a mistake, and could be foolish, such as when his poorly drawn creations caused accidents. He laughed with a unique "Ka, ka, ka." However, this personality was a complete fabrication. In truth, his loyalty was solely to the Kurozumi Family, and he harbored no genuine attachment to the Kozuki Family. He viewed his role as a retainer as a performance he was meant to see through to its end, ideally by dying alongside them. When his true nature was revealed, he became merciless, sadistic, and taunting, showing no remorse for his betrayal and cruelly mocking his former allies.

Kanjuro's primary motivation was not a desire for power or personal gain, but a deep-seated wish for revenge and a place to die. His parents' unjust death at the hands of Wano's citizens filled him with a desire for vengeance against the Kozuki and their supporters. Orochi gave him the means to achieve this by making him a spy, and Kanjuro was determined to see his family's persecutors fall, even if it cost him his own life. His role in the story is that of a complex antagonist and a major villain during the Wano Country Arc. For much of the narrative, he is presented as a valuable ally to the Straw Hat Pirates and a fellow member of the Nine Red Scabbards, the loyal retainers of Kozuki Oden. His secret purpose was to feed information to Orochi and Kaido, sabotaging the Kozuki family at every turn. He was responsible for leaking the location of his comrade Raizo to the Beast Pirates, which led to the destruction of the mink tribe's land of Zou, and he informed Orochi of the alliance's plans during the raid on Onigashima.

Kanjuro's most significant relationship is with his master, Kurozumi Orochi, whom he served unwaveringly. He was a trusted spy and key instrument in Orochi's rise to power. His other key relationships are with the Kozuki Family, a web of deception he maintained for decades. Lord Kozuki Oden trusted him as a retainer. He befriended the other Red Scabbards, particularly Kin'emon, who considered him a dear comrade and brother. When his betrayal is revealed, this relationship turns into one of bitter conflict. Kanjuro coldly states he bore no hatred for them, but his actions were those of a man utterly dedicated to their destruction, causing immense emotional pain to those who had trusted him.

Kanjuro's character development is marked by a shocking reversal. For hundreds of chapters, he is portrayed as a quirky, loyal, but somewhat incompetent ally. His development culminates in the revelation that his entire personality was a facade, a role he played perfectly. The final stage of his development sees him fully embrace his role as a villain, attempting to kill his former friends with a painted copy of their beloved master, Oden. He is lethally wounded by Kin'emon, and in his final moments, he remains committed to his performance, seeking a memorable end to his life's act. Even in death, his actions had the potential to cause massive destruction, forcing his former allies to contend with his lingering malice.

Kanjuro possesses several notable abilities. He ate a Paramecia-type Devil Fruit, the Brush-Brush Fruit, which allows him to bring anything he draws to life as a three-dimensional, real object. The creations can be living creatures or functional items like ladders, and he can even use the power to hide himself within surfaces as a drawing. His primary tool is a giant brush shaped like a sword. A critical detail is that he is left-handed. For years, he deliberately used his non-dominant left hand to draw crude, flawed, and often comically useless creatures to hide his true skill. With his dominant right hand, he can create highly detailed, photo-realistic paintings that are incredibly powerful and indistinguishable from reality. He is also proficient in using Busoshoku Haki, a form of spiritual armor, which he used to reinforce his brush and help push back Doflamingo's deadly Birdcage.