Katana is an eighteen-year-old boy who operates within the criminal underworld of Night Town. His appearance is distinctive and somewhat gothic, marked by a tall and narrow frame that is gaunt and deathly pale. He has black hair that reaches his neck and sharp yellow eyes, with a notable scar located beneath his left eye, the origin of which remains unknown. His typical attire consists of a schoolboy-inspired outfit including a striped shirt, a sweatervest, a tie, and slacks, all worn under a long trench coat. He makes his home in a solitary manner, living on the garage-level of an abandoned building situated on the edge of a junkyard.

In terms of personality, Katana is characterized as the quiet type, being dark, cold, and stoic by nature. He prefers to live alone for the most part, seemingly having no friends and expressing little desire for any. While not inherently evil, his worldview and behavior align with those of a sociopath, showing little interest in anything beyond money and the drive to ascend the criminal hierarchy. He functions as a primary anti-hero, often serving as an antagonist to the main characters while also swinging unpredictably between the roles of villain and ally depending on his ever-shifting mood and immediate circumstances. He is described as ruthless, aggressive, and having a competitive streak, preferring to operate in a solitary and aloof manner. His grand ambition is to use violence to rule over Night Town and eliminate any rivals.

Before obtaining his own special powers, Katana worked as a mercenary or a man-for-hire, earning his living by piloting a Heavy Metal, a type of large, illegal mechanical contraption. He would take on jobs from various criminals, including the Jacque Bruno gang, serving as their muscle. This path changes after a pivotal encounter with the protagonist, Hajiki. During a confrontation, Hajiki's Techode, Lightning, defeats the Heavy Metal that Katana was piloting. Following this defeat, Katana comes into possession of a Gad, a mysterious cube-like object, which transforms into his own personal Techode, which he names Zero. Zero is a large, black, humanoid robot that responds to Katana's thoughts and desires, reflecting his inner drive for power and dominance.

Katana's primary role in the story is as the main rival to Hajiki. Their conflict stems from opposing philosophies; Hajiki represents a hardworking and cooperative approach to life, while Katana embodies a "might makes right" attitude, seeking to eliminate anyone he perceives as a problem or an obstacle to his own rise. He sees Hajiki as a direct rival after his defeat and is determined to prove his own superiority. Another significant relationship is with Takumi Kisaragi, a wealthy boy from Gold Town who acts as a self-appointed vigilante. Takumi is obsessed with justice and views Katana as his polar opposite and the embodiment of pure evil, frequently referring to him as a beast raised in violence. Unlike Takumi, who sees Katana as a personal nemesis, Katana regards Takumi merely as a persistent and annoying pest, whom he has no hesitation in beating severely when provoked.

The most unique and revealing relationship in Katana's life is with a young girl named Sayuri. She appears seemingly out of nowhere, dressed in a pink coat and carrying a bunny plush toy, and she stubbornly insists on being his friend, following him everywhere with a persistent smile and cheerful demeanor. Despite his initial cold resistance and attempts to drive her away, Katana gradually adapts to her presence. It is eventually revealed that Sayuri is not an ordinary girl but a humanoid Techode, created from the same Gad substance as Zero. She is a manifestation of Katana's own subconscious, embodying a cherished childhood companion from his past and acting as a poignant reminder of his inherent loneliness. She represents the only entity that he has fully embraced, and her presence serves as a testament to his innate, buried capacity for affection and connection. Through his bond with Sayuri, a change in Katana's internal state becomes noticeable, especially after her eventual disappearance from his side.

Katana experiences development primarily through his rivalry with Hajiki and his connection to Sayuri. He initially contemplates watching Hajiki fall into the darkness of the criminal world as a way to validate his own nihilistic path. However, Hajiki's choices and the eventual fading of Sayuri from his life, which occurs when she is no longer needed as he grows more self-reliant, bring about a shift in his psychological landscape. His journey involves moving from a purely mercenary and power-hungry figure to someone whose cold exterior is forced to reckon with the bonds he forms, however reluctantly.

Regarding his abilities, Katana is a highly skilled pilot of Heavy Metals even before acquiring a Techode, being considered one of the best operators. His primary power comes from his Techode, Zero, which he trains with and uses to enforce his will and fight his battles. Unlike some other Techode users, Katana is driven and methodical, using his mech as a tool to systematically achieve his ambition of controlling Night Town.