Kō Murakami is a third-year student at Tamakoma Second’s affiliated school and a member of the elite Tamakoma Branch of Border, specifically serving as the ace of Tamakoma Second. He stands out physically with a tall, athletic build, dark brown hair typically kept short and neat, and calm, steady eyes. His uniform is often worn in a relaxed manner, reflecting his easygoing but disciplined nature.

Background wise, Kō was an early generation Border trainee who came up alongside other skilled agents like Sōya Kazama and Shun Midorikawa. He is recognized as one of the most talented sword users in Border, earning a reputation for his prodigious skill with the Kogetsu trigger. Unlike many who rely purely on reflexes or strategy, Kō’s approach to combat is built on an exceptional sense of timing and distance control, honed through countless hours of practice.

Personality wise, Kō is reserved, polite, and levelheaded. He seldom raises his voice or shows dramatic emotion, preferring to observe and analyze before acting. Despite his calm exterior, he holds a fierce competitive drive and a deep respect for strong opponents. He is not arrogant about his abilities but carries a quiet confidence that can be mistaken for aloofness. He values teamwork and loyalty highly, often putting his squad’s success above personal glory. Kō is also notably empathetic, quick to offer praise to allies and foes alike when they demonstrate skill or growth.

Motivation and role in the story center on his desire to strengthen Tamakoma Second and help the team reach the top ranks of Border. Unlike some agents driven by revenge or glory, Kō fights to prove that teamwork and dedicated training can overcome raw talent or numbers. He acts as a stabilizing force for his squad, balancing the more impulsive Osamu Mikumo with tactical advice and steady support in combat. His presence gives Tamakoma Second a reliable ace who can stand toe-to-toe with high-rank attackers.

Key relationships include his captain, Yūma Kuga, whose unconventional combat style and overwhelming instinct initially unsettle Kō, but they develop a strong mutual respect through joint battles. With Osamu Mikumo, Kō serves as a mentor figure, offering training advice and tactical observations without condescension. He shares a friendly rivalry with agents like Sōya Kazama, who acknowledges Kō’s abilities, and he maintains a courteous but competitive dynamic with the top attackers of other squads, such as Tōichirō Yūki and Ken Satori.

Development in the story sees Kō moving from a solo-oriented prodigy to a more team-focused fighter. Early on, he relies heavily on his individual technique and reactions, but as Tamakoma Second faces stronger opponents, he learns to coordinate more closely with Osamu’s strategies and Yūma’s unpredictable maneuvers. He also matures as a leader, offering encouragement and tactical adjustments during high-pressure rank wars. Notably, he begins to incorporate more adaptive tactics, such as using his Kogetsu’s shields and wire formations in ways he previously dismissed as unnecessary for a pure attacker.

Notable abilities center on his mastery of the Kogetsu attacker trigger, specifically his signature technique: the silent knife, a quick-draw slash delivered from the sheathed blade that minimizes telegraphing. He possesses top-tier trion levels for an attacker, allowing him to maintain his Kogetsu’s durability and produce strong blade shields. His footwork and spatial awareness are exceptional, enabling him to control engagement distances precisely. While not a gunner or shooter, he has solid fundamentals in defensive trigger use, particularly in deploying Escudo to protect allies or block escape routes. His combat style is methodical and precise, focusing on minimal wasted motion and capitalizing on split-second openings. In team battles, he often takes the role of a solid anchor, holding key positions while allowing Yūma to roam or Osamu to set traps.