Yuuma Kuga

Yuuma is relaxed, blunt, curious, and difficult to intimidate. Because he has spent much of his life outside Japan, he initially lacks familiarity with local customs, school culture, traffic rules, and ordinary social conventions. This creates misunderstandings, but he adapts quickly and rarely becomes embarrassed by what he does not know.

His practical worldview comes from growing up in countries where warfare with Triggers was commonplace. When Osamu risks himself against a Marmod to protect classmates, Yuuma initially points out that charging into a fight he cannot win may simply result in another casualty. He is not indifferent to strangers; he simply approaches danger through calculations shaped by years of actual warfare.

Yuuma dislikes arrogance and bullying, particularly when someone stronger abuses people who cannot fight back. He generally remains cheerful while humiliating opponents who deserve it rather than becoming openly angry. Around people he trusts, he is playful and frequently participates in teasing, especially when another person's reactions are easy to provoke.

He also has a strong sense of personal obligation. Promises made by his father carry enormous weight, and Yuuma does not casually abandon people who have accepted him. This loyalty is especially visible in his refusal to take command of Tamakoma Second himself, insisting that Osamu remain captain even though Yuuma is unquestionably the stronger fighter.

Yuuma is an elite close-range combatant whose experience predates his Border membership. His father trains him in real battles across the Neighborhood, giving him instincts that ordinary C-Rank recruits cannot acquire through simulations. He reads an opponent's habits quickly, adapts during exchanges, and rarely becomes fixated on a single attack pattern.

Within Border, Yuuma specializes in Scorpion, the shape-shifting Attacker Trigger. He commonly forms blades from different parts of his body, creates unconventional angles of attack, and combines multiple Scorpions into specialized forms. His flexibility makes him especially difficult to predict because he treats Trigger configurations as tools rather than fixed techniques.

His Side Effect allows him to detect lies. When someone deliberately says something they know to be false, Yuuma experiences a distinctive sensation that alerts him to the deception. It does not reveal the truth automatically and cannot replace ordinary deduction, but it makes conventional bluffing against him difficult.

Yuuma also possesses a Black Trigger created through extraordinary circumstances involving his father. The Trigger allows him to analyze and reproduce the functions of other Triggers through seals, then strengthen or combine those effects. Replica assists him in processing and operating its more complicated functions.

Yuuma's human body is actually kept in suspended condition within a Trion-based body after he suffered a fatal injury in the Neighborhood. Yuugo sacrificed himself to create the Black Trigger that preserved his son, leaving Yuuma's physical condition dependent on the Trigger and causing his apparent body to stop aging normally.

Yuuma transfers into Osamu's school after arriving in Japan to search for information about Border and a person his father once knew. His complete lack of fear toward Neighbor attacks immediately distinguishes him from ordinary civilians, while his unfamiliarity with Border's rules creates problems once Osamu realizes he is a Neighbor himself.

After becoming involved with Tamakoma, Yuuma learns that the Border organization his father knew has changed considerably. Yuuma Kido's faction is openly hostile toward Neighbors, while Tamakoma maintains relationships with friendly Neighbor nations. Yuuichi Jin and Takumi Rindou help protect Yuuma from agents seeking his Black Trigger.

Yuuma joins Border after Replica asks Osamu to give him a new goal. He becomes part of Tamakoma Second with Osamu and Chika Amatori, participating in B-Rank Wars so the squad can qualify for Border's Away Team selection.

During Rank Wars, Yuuma becomes Tamakoma Second's principal point scorer. His individual skill is already near the level of elite Border Attackers, but the competitions force him to learn the organization-specific tactics, map systems, Trigger combinations, and team coordination that experienced Border squads take for granted.

The Large-Scale Invasion gives Yuuma an opportunity to fight enemies from Aftokrator using the experience accumulated in the Neighborhood. His knowledge of Neighbor warfare proves particularly important when Border encounters humanoid combatants whose Trigger technology exceeds ordinary Trion Soldier tactics.

After Replica is separated from him during the invasion, Yuuma loses the partner who had accompanied him since his father's sacrifice. He continues pursuing Tamakoma Second's expedition goal partly because reaching the Neighborhood offers the possibility of finding Replica again.

Osamu Mikumo is Yuuma's first close friend in Mikado City and later his captain. Yuuma quickly recognizes that Osamu Mikumo is physically weak but respects his determination and judgment. When Osamu suggests that Yuuma should lead Tamakoma Second, Yuuma refuses and insists that the squad exists because Osamu brought its members together.

Yuugo Kuga is Yuuma's father, teacher, and greatest formative influence. Yuugo Kuga teaches him combat, the principles for dealing with other people, and several rules about how to live in dangerous environments. His sacrifice creates the Black Trigger that keeps Yuuma alive after his mortal injury.

Replica is Yuuma's autonomous Trion Soldier companion and effectively a member of his family. Replica assists him in combat, explains information about the Neighborhood, and helps operate the Black Trigger's more complicated seals.

Chika Amatori becomes Yuuma's teammate and friend in Tamakoma Second. Yuuma treats her enormous Trion as an advantage rather than something frightening and frequently works around her reluctance to shoot people without criticizing her for it.

Yuuichi Jin is one of Yuuma's earliest Border allies. Yuuichi Jin uses his foresight to protect Yuuma and his Black Trigger from Border's hostile faction and understands that Yuuma can become an important asset rather than an enemy.

Konami Kirie becomes one of Yuuma's combat mentors at Tamakoma. Konami Kirie is stronger than him in their early training matches, giving Yuuma an experienced opponent capable of correcting weaknesses that ordinary recruits cannot expose.

Hyuse begins as an Aftokrator enemy but later becomes Yuuma's teammate. Both are Neighbor-born fighters with extensive real combat experience, allowing Hyuse and Yuuma to understand each other's tactical thinking unusually quickly.