Combat Agent Six, known as Agent Six or simply Six, fights for the Kisaragi Corporation—an Earth-conquering entity pursuing interplanetary domination. His real name remains undisclosed. He joined Kisaragi as a part-time employee at age nineteen during his first year of high school, roughly three to four years pre-storyline. Severe injuries sustained shielding Kisaragi leaders from a Hero necessitated life-saving surgeries that transformed him into a combat agent. These procedures implanted cybernetic enhancements: a translation chip, regenerative capabilities, night/underwater vision, ten-minute breath-holding, environmental adaptation, and three-minute space survival. Immuno-boosting nanomachines in his bloodstream grant disease resistance.

Six operates with pragmatic slyness, favoring underhanded tactics like hostage-taking or distraction exploitation. He habitually commits petty crimes—sexual harassment and exhibitionism—to earn Kisaragi’s "Evil Points," spent on snacks, pornography, and video games. Though lecherous, cowardly, and prone to complaint, he rigidly follows Kisaragi regulations and orders. As an early member and senior agent, his soft-hearted reluctance toward genuinely evil acts impedes promotion. He demonstrates fierce loyalty, refusing to abandon comrades during crises like aiding Snow to rescue Grimm and Rose. This inherent kindness clashes with his villainous role, branding him a "Minion with an F in Evil." Memory lapses cause him to recall emotional milestones but forget minor misdeeds or traumas.

Frugal with Evil Points, Six employs outdated gear: first-generation power armor boosting strength to superhuman levels, equipped with cooling and camouflage systems. Standard loadout includes a combat knife, pistol, and teleporter wristwatch for equipment summoning. His signature weapon is the Anti-Armored-Vehicle Vibrating Bat Sword Type-R (R-Buzzsaw), which vibrates to slice through materials. He occasionally uses an anti-material rifle and suppression grenades. His physicality operates at human limits, augmented by cybernetics.

Relationships define Six’s world. He shares a sibling dynamic with combat android Alice Kisaragi, acting as her pragmatic foil. He harbors romantic feelings for Supreme Leader Astaroth, drawn by her smile and aspiring to marry her. With colleague Belial, he exchanges mutual sexual harassment; Lilith irritates him with her selfishness. In the fantasy world, he bonds with Kingdom of Grace allies: he sexually harasses yet protects Grimm, pledging marriage if both are single in a decade; he clashes but cooperates with Snow; and he gains the trust of Rose, who calls him "commander." He sexually harasses demon commander Heine while treating her as a subordinate. He scorns the Strategist as authentically cowardly without merit.

Six evolves from self-interest to prioritizing new-world allies. Initially obsessed with hoarding Evil Points, he later spends them and risks his life to save others—like reviving Grimm post-mortem. He forfeits returning to Earth to protect the Kingdom of Grace, revealing latent altruism. This shift echoes his abandoned dream of heroism, discarded pre-Kisaragi due to self-doubt. Leaders like Astaroth recognize his leadership potential in morale-building and conflict resolution. Despite flaws, his actions increasingly unveil a "Hidden Heart of Gold," balancing villainy with loyalty and protection.