Ichimatsu is the main protagonist of the Samurai Gun narrative, a figure defined by the sharp contrast between his daytime anonymity and his nighttime role as an agent of violent justice. His appearance is distinct and marks him as unusual within the setting: he has silver-white hair, a consequence of his mixed-race heritage, and he wears an eyepatch over one eye, making him a one-eyed samurai in the tradition of legendary figures like Jubei. During daylight hours, he blends into the fabric of his community by working at a local tavern, a humble cover that allows him to observe the flow of daily life without drawing attention to himself. When he acts as the Samurai Gun, however, he dons a helmet and protective gear typical of his clandestine group, transforming into a symbol of retribution against the shogunate's oppression.

Personality-wise, Ichimatsu is a study in internal conflict. He presents a blunt and somewhat weary exterior, often complaining about the missions he is given and expressing a deep reluctance to kill, stating that he is tired of the bloodshed. This reluctance, however, is consistently at odds with his actions; when the situation demands it, he becomes a precise and unflappable killer, dispatching his targets without hesitation and earning a reputation as the most deadly member of the Samurai Gun group. This contradiction suggests a man who is deeply uncomfortable with his own nature yet unable to escape it. Despite his hardened demeanor, there is a hint of underlying kindness, particularly in his interactions with certain individuals, even if he is emotionally guarded and sometimes oblivious to the affections of others.

His primary motivation is rooted in a traumatic past that haunts him constantly, manifesting in recurring nightmares. As a child, he was forced to witness the rape and murder of his sister at the hands of a man who took pride in the act, and his mother was also killed in the same incident. This horrific memory has instilled in him a burning desire for revenge against the specific individual responsible, and this quest is the central fire that keeps him involved in the dangerous life of a Samurai Gun. His motivations are further complicated by his relationship with the mysterious Council, the organization that directs the Samurai Gun. He suspects that this Council may have been involved in the death of his family, making his service to them a means to uncover the truth, while simultaneously being trapped in servitude, as he knows that quitting would likely lead to him being hunted down.

In the overall story, Ichimatsu functions as the primary operative of the Samurai Gun, a group of rebels fighting against an abusive shogunate that uses beatings, imprisonment, and murder to maintain its reign of fear. His role is to receive orders from the Council and carry out missions that are often secretive and morally ambiguous, such as assassinations and sabotage, far removed from the ideals of a chivalrous hero and more in line with a dark avenger or contract killer. His key relationships are with other members of his cell. He works closely with Daimon, a fellow Samurai Gun who works as a schoolteacher by day and is a close friend, despite their differing attitudes toward their work, with Daimon embracing the role more enthusiastically. Another colleague is Kurenai, a woman who works alongside Ichimatsu at the tavern and is also a skilled fighter, often participating in missions. Central to his personal life is Ohana, a woman who works at a brothel and later at the tavern. She is deeply in love with him and cares for him, but Ichimatsu remains emotionally distant, never sleeping with her due to the deep-seated psychological issues and trauma stemming from his sister's sexual assault.

Throughout the narrative, Ichimatsu undergoes a cyclical, rather than progressive, form of development. He repeatedly insists that he will not kill again, only to find himself drawn back into violence by circumstance, a sense of duty, or the pursuit of his revenge. His core ethical dilemma remains largely unresolved; he continues to struggle with the question of whether his actions are justice or if they make him no different from the murderers he hunts. He remains trapped between his desire for a peaceful life and his inability to let go of his past, serving a shadowy organization that he does not fully trust in the hopes of achieving his personal vengeance. His notable abilities are primarily centered on his combat prowess. He is highly trained in the use of firearms, and his skills are such that he can face enemies armed with submachine guns using only his revolvers. He also possesses incredible speed and agility, allowing him to dodge bullets and arrows. In his role as Samurai Gun, he sometimes employs tools like sleeping incense to incapacitate enemies without killing them, offering a brief reprieve from his otherwise lethal methodology.