Aza Chōbee, also known as the Bandit King of Iyo, is a young man who leads a notorious gang of criminals. He stands at 176 centimeters tall and is twenty years old, with a muscular build, spiky blonde hair often tied with a small braid, and a significant portion of his face covered by scars that have also claimed his right eye. His rough appearance is a testament to a violent life, but his origins lie not in the criminal underworld but in a fallen samurai family. Chōbee and his younger brother Tōma were born as sons to a retainer of the Akō Domain, but after their lord was forced to commit seppuku, the family lost their status and fell into poverty. Following the death of their mother from illness and the execution of their father, the two brothers were kidnapped by bandits. In a turn of events that speaks to his inherent ferocity and cunning, Chōbee managed to take control of the gang, eventually rising to become their feared leader.

On the surface, Chōbee displays an arrogant, cruel, and extremely violent nature. He prefers to solve problems with brute force rather than words and takes a sadistic pleasure in combat. This violent exterior, however, masks a sharp and calculating intellect. Chōbee is a rational thinker and a master of reading people and situations, allowing him to adapt to even the most dire circumstances. His core motivation is the survival and protection of his younger brother, Tōma, who is his only remaining family. This singular devotion is the guiding principle behind all his actions, from his rise as a bandit to his decisions on the mysterious island. He is driven by a deep pragmatism, believing that the ability to adapt to one's environment is the true measure of strength, and he is willing to lie, scheme, or form temporary alliances with anyone if it ensures his and his brother's survival.

In the story, Chōbee is one of the death row convicts sent on a mission to find the Elixir of Life in exchange for a pardon. He is accompanied and supervised by his brother, Tōma, who serves as his executioner from the Yamada Asaemon clan. Their relationship is the most significant and defining aspect of his character; Chōbee’s love for Tōma is genuine and absolute, and he willingly endures humiliation and takes any risk to keep him safe. He forms key relationships based on mutual need, respecting formidable fighters like the swordsman Tamiya Gantetsusai, and he is not afraid to ally with rivals like the ninja Gabimaru when their goals align. Unlike many other characters who undergo profound moral transformations, Chōbee’s development is remarkably consistent. He remains true to his core nature from beginning to end: a brutal, calculating, and fiercely devoted bandit king. His growth is less about changing who he is and more about the increasing lengths to which he will go to uphold his singular philosophy of survival alongside his brother.

Chōbee is an exceptionally formidable fighter, possessing immense physical strength that allows him to crush a man's neck even with his arms bound or wield a massive axe with ease. He has a high tolerance for pain and is a perceptive combatant, able to analyze situations quickly and formulate effective strategies mid-battle. His most notable ability is his unique and rapid adaptation to the island's supernatural energy, known as Tao. He was the first human to instinctively grasp the concept of Tao without formal training. By harnessing this power, he can push his physical abilities far beyond normal human limits. This adaptation eventually leads to a partial "flowerization" transformation, where his body takes on plant-like characteristics and gains regenerative abilities similar to the island's immortal masters, the Tensen. This process dramatically alters his appearance, darkening his skin and causing vine-like growths to emerge from his body, but his will and singular focus on protecting his brother remain unshaken.