Gren is a central figure in the narrative, primarily defined by his role as a mentor and the catalyst for the protagonist’s journey. He is a full-fledged, veteran bounty hunter working for the Ghomvak Security & Investigations agency. Often referred to as Iria’s older brother, the precise nature of their relationship is left somewhat ambiguous. While he is consistently presented as her sibling, a fellow hunter named Fujikuro hints that he might instead be a close older male figure, using the Japanese term onii-san, which can denote either a biological brother or a respected guardian. Regardless of the exact血缘关系, Gren is the single most important person in Iria’s life, having taught her nearly everything she knows about the hunting trade and serving as her direct supervisor during her apprenticeship. His appearance mirrors Iria’s to a degree, as he is depicted wearing a blue cloak and hair beads similar to hers. He also possesses a unique pendant, an item that later becomes a significant clue for others searching for him.

In terms of personality, Gren is portrayed as a capable and seasoned professional, a stark contrast to the reckless and inexperienced Iria at the story’s outset. His decision-making is driven by a strong sense of duty and a willingness to make the ultimate sacrifice. This is most evident during the disastrous mission on the spaceship Karma. When the team’s target, the near-invincible alien Zeiram, proves unstoppable, Gren makes the split-second decision to stay behind and destroy the entire ship in a desperate attempt to kill the creature, seemingly giving his own life in the process. This act of self-sacrifice is his primary motivation within the story’s events, showcasing a protector’s instinct not just for his sister, but for the greater good. He is a man of action and conviction, whose skills as a hunter are respected enough that he is entrusted with high-profile, dangerous assignments, such as the rescue mission on the Karma for the powerful Tedan Tippedai corporation.

Gren’s role in the story is twofold. Initially, he serves as the experienced anchor for Iria, providing her with a goal and a standard to aspire to. His apparent death in the first episode is the inciting incident that transforms Iria from a mere apprentice into a driven, independent heroine. Her entire quest throughout the series is fueled by the desire to uncover the truth about the Karma incident and to find out what happened to him. However, his most significant narrative function occurs later in the series, through a dramatic and tragic development. It is ultimately revealed that Gren did not die in the explosion. Instead, he survived but was captured and assimilated by the alien Zeiram. This assimilation represents a horrifying fusion; Zeiram, which needs to absorb other life forms to sustain itself and potentially learn what they know, incorporates Gren into its own being.

This development leads to a unique and painful conflict, as Iria is forced to confront Zeiram, which can now use the form and perhaps even the abilities of her beloved brother against her. The presence of Gren within Zeiram creates a deep psychological horror for Iria, as her battle transforms from a simple hunt for a monster into a desperate struggle to possibly save or, failing that, to find closure for the person she admired most. His relationships are therefore central to the plot: his bond with Iria is the emotional core of the anime, his partnership with the agent Bob is crucial to the initial mission, and his assimilation into Zeiram creates the series’ most personal and frightening antagonist. Gren’s notable abilities, while not extensively detailed, are implied through his status as a veteran hunter. He is skilled enough to lead a dangerous mission and is respected by his peers. However, his ultimate demonstration of ability is a tragic one, as his own physical form and knowledge become weaponized against humanity after his assimilation by Zeiram.