**Kōhei Izumi** spearheads as the No. 2 Shooter in Border and a key member of the Tachikawa Squad, operating from Border headquarters. He possesses average height, dark blond hair falling to his neck, and distinctive golden eyes. In combat, he dons the standard Border long coat—black with thin red stripes and a Border emblem patch on the left sleeve, matching his squad.

Izumi exhibits a personality marked by reckless impulses tempered by strategic intelligence. He demonstrated this blend by proposing to annihilate an entire battlefield with Meteor to flush out the Arashiyama Squad. Squadmate Tōma observes his frequent conception of harsh or unorthodox tactics. Despite this impulsiveness, Izumi displays humor in both casual and combat situations and shows immaturity among friends, while his underlying strategic acumen is acknowledged.

Functioning as a Shooter, Izumi bypasses conventional firearms, directly forming trion into cubes for projectile attacks. His expertise encompasses multiple bullet modes: Asteroid (standard rounds), Viper (maneuvering rounds with sharp turns), Hound (tracking rounds), and Meteor (wide-area explosive rounds). He discovered composite bullets—hybrid rounds merging two bullet types—through experimental impulse, earning him descriptors like "genius-like" and "bullet idiot," highlighting his deep engagement with Trigger mechanics.

Notable trivia includes his preference for fried prawns, croquettes, oranges, and employing Full-Attack maneuvers. His surname "Izumi" translates to "Flood," and "Kōhei" means "Fairness" or "Justice." He ranked fifth in Border's first Valentine's Day poll but claimed first place in the subsequent ranking. Additional details specify a September 21 birthdate (Virgo), blood type B, and a height of 175 cm.