Choso is a central figure in the narrative, introduced as a powerful antagonist whose loyalties undergo a profound transformation. He is the eldest of the nine Death Painting Wombs, special-grade cursed objects that, when incarnated, become hybrids of human and cursed spirit. His creation was an unnatural experiment orchestrated by the ancient sorcerer Kenjaku, who used the blood of Noritoshi Kamo, a member of a prestigious jujutsu clan, and a human woman with a unique constitution who was the mother of the Death Paintings. This complex origin grants Choso a unique perspective, viewing himself as having three parents. He existed as a conscious cursed object for over a century and a half, during which he continuously refined his innate abilities long before obtaining a physical body.

In terms of personality, Choso is typically calm, reserved, and aloof, often appearing disinterested or bored in his surroundings. He does not possess the inherent malice toward humans that many cursed spirits do. However, this placid exterior masks an intense and unwavering dedication to his family. His entire identity is built around his self-assigned role as the eldest brother. He is fiercely protective of his younger siblings and is driven almost entirely by his love for them. This devotion is his greatest strength and his most defining characteristic. He cannot tolerate those who bring harm to his family, and his hatred is reserved specifically for Kenjaku, the being who toyed with his mother and brothers lives.

Choso's primary motivation evolves drastically over the course of the story. Initially, he is driven by a desire for revenge. After sensing the deaths of his two younger brothers, Eso and Kechizu, at the hands of Yuji Itadori and Nobara Kugisaki, he vows to kill their murderers. He joins the cursed spirits' plan during the Shibuya Incident solely for the opportunity to exact this vengeance. However, during his final confrontation with Yuji, a strange phenomenon occurs. Due to a side effect of his blood manipulation technique and his unique constitution as a Death Painting, Choso experiences a surge of fabricated memories that cause him to perceive Yuji as another one of his younger brothers. This realization shatters his previous motivations. He abandons his revenge and immediately switches his allegiance to protecting Yuji, declaring himself Yuji's older brother and shifting all his hatred and blame onto Kenjaku, whom he now sees as the true enemy.

During the events of the Culling Game, Choso role becomes that of a key ally to the protagonist group. Having been accepted by Yuji and his friends, Choso works alongside them to thwart Kenjaku's plans. His vast experience and power earn him a significant responsibility; he is chosen by the ancient sorcerer Tengen to act as a guard, a role typically reserved for special-grade sorcerers, which officially recognizes his immense capabilities. In this capacity, he devises a strategic two-part plan to fight Kenjaku alongside the special-grade sorcerer Yuki Tsukumo. His primary task is to engage Kenjaku first in a high-stakes battle, aiming to force his opponent to reveal his innate techniques before Yuki joins the fray, demonstrating his tactical intellect and willingness to sacrifice himself for the greater good.

Choso key relationships are the primary drivers of his character arc. His bond with his deceased brothers, Eso and Kechizu, haunts him; he carries immense guilt for having forced them to live as curses, believing he took away their choices. His newfound relationship with Yuji Itadori becomes his new purpose. He forgives Yuji for killing his brothers, understanding it was not an act of malice, and dedicates himself entirely to Yuji protection and growth. His relationship with Yuki Tsukumo is also crucial, as her advice to live as a human, not a curse, deeply influences him and helps guide his path forward. Conversely, his relationship with Kenjaku is one of pure antagonism, viewing him as an unforgivable figure who must be stopped.

Choso development is significant, tracing a path from a vengeful tool of curses to a self-sacrificing protector of humanity. He confronts his own regrets and guilt, choosing to move forward and embrace a new family rather than remain trapped in the past. His final decision to live as a human for Yuji sake represents a complete transformation from his origins as a cursed womb.

Choso notable abilities are formidable, centering on his mastery of the Kamo clan hereditary technique, Blood Manipulation, which he has perfected over 150 years of meditation as a cursed object. His control over this technique far surpasses that of the current Noritoshi Kamo. His hybrid nature grants him a unique advantage: he can convert his cursed energy directly into blood, meaning he cannot die from blood loss as long as his cursed energy holds out. His own blood is also highly toxic to humans. His techniques include Piercing Blood, where he condenses blood to its limit and fires it at supersonic speeds like a bullet; Supernova, an original technique he developed that detonates compressed blood orbs for a shotgun-like, omnidirectional blast; and Flowing Red Scale, which he uses to manipulate his own physiology—increasing his body temperature, pulse, and red blood cell count to drastically enhance his physical strength and speed. He can also harden his blood into a blade for close combat. Demonstrating his tactical genius and deep love for his brothers, Choso is even able to replicate the unique abilities of Eso and Kechizu in the heat of battle, using them in creative ways to gain an advantage over powerful opponents.