Bunji Kugashira holds a significant place within the narrative of Gungrave as a talented and driven individual whose path is inextricably linked to that of the protagonist, Brandon Heat, also known as Beyond the Grave. Bunji is introduced as a highly skilled gunman who eventually rises to become one of the Big Four, the elite executives of the powerful mafia organization known as Millennion. His early history in the organization is defined by his role as the sole shatei, or younger brother figure, to Brandon, for whom he develops a deep sense of admiration and respect for both his character and his formidable abilities. A defining moment in their early relationship occurs when Bunji challenges Brandon to an unarmed fight as a condition for joining Millennion; Brandon's victory secures Bunji's loyalty and cements his status as Brandon's first apprentice, one who seeks to embody the organizations Code of Iron.

Personality-wise, Bunji Kugashira is a complex figure governed by a peculiar sense of morals. Despite operating in a world of violence, he exhibits extreme loyalty to those he serves, though his loyalty is often more focused on individuals like Harry McDowell than on the abstract concept of the organization itself. He adheres to a strict, personal version of the Code of Iron, which prioritizes loyalty above all else, leading him to execute a fellow member not for betraying Millennion, but for betraying Harry personally. This fierce loyalty is matched by a ruthless and pragmatic demeanor; over the years, he develops a habit of indiscriminately killing subordinates he deems useless and prefers to work alone. His character is also marked by a certain world-weariness and a sardonic edge, as seen in his near-constant habit of smoking a cigarette and, after being resurrected as a Deadman, his cynical complaints about his new existence and the poor sense of humor of those who revived him. His relationship with Brandon is the primary driver of his motivations, evolving from pure admiration to a complex blend of friendship, resentment, and an obsessive desire to surpass his mentor.

In the overall story, Bunji serves as a direct rival to Beyond the Grave and a recurring obstacle. After Brandon is betrayed and resurrected as the memory-impaired Deadman known as Grave, Bunji refuses to accept that his aniki is truly gone. He harbors a deep-seated discontent and, believing Brandon betrayed Millennion, takes the news harshly, which fuels his actions. This leads to several key confrontations across the series. In the original Gungrave, he challenges Grave in a final, desperate gunfight but is defeated. In Gungrave: Overdose, he is resurrected as a Deadman by the Corsione Family and, despising his new state, dedicates himself to seeking revenge on Grave again, only to be defeated once more. In Gungrave G.O.R.E., the cycle continues as he is resurrected for a third time by a mysterious entity, this time completely stripped of his emotions and memories, yet he is fated to face Grave once again. His role is not merely that of an antagonist; he is also a mirror to Grave, representing the destructive nature of obsession and the inability to let go of the past. Key relationships defining his character include his brotherly rivalry with Brandon, his complicated loyalty to Harry McDowell, and a later connection to Jyuji Kabane, who is revealed to be his younger brother.

Throughout his appearances, Bunji undergoes a tragic form of development that is less about personal growth and more about a cyclical pattern of death and resurrection. In life, he was a legendary hitman who sought to prove himself against the standard set by Brandon. After his first death, his development is arrested; each resurrection brings him back in a more diminished state. In Overdose, he is a depressed and reluctant Deadman who hates his existence, noting that his only remaining purpose is to fight. By G.O.R.E., he is reduced to an empty shell, resurrected without the memories and emotions that once defined his intense rivalry, representing the ultimate loss of self that comes from an unending cycle of violence. Notably, in the anime adaptation, he is shown to regain a sliver of his former respect for his mentor after his final defeat, adopting Brandons signature finger taunt as a gesture of acknowledgment before his body breaks apart.

As a combatant, Bunji is an exceptionally talented marksman and gunman, renowned enough to be called The Wolf or Madman for his excellent skills in battle. He is frequently seen wielding a Browning Hi-Power pistol modified with a large drum magazine. Unlike other characters who undergo grotesque physical transformations when enhanced through Necrolyzation, Bunjis Superior form is more subtle and refined; he exhibits no outward physical change but instead becomes significantly faster, more accurate, and stronger, effectively gaining a suite of abilities that mirror Beyond the Grave himself. In the games, this translates to a playstyle that is similar to Graves but noted for being more agile.