Kazuma Satomi serves as the No. 1 Gunner in Border's Kusakabe Squad. His appearance features a spiked crewcut accentuated by a widow's peak, thin arched eyebrows, and distinctive fluorescent orange glasses shaped like swimming goggles. His laughter often reveals an unhinged jaw, while his resting expression sometimes forms a cat-like curve on his upper lip.

He wears a black long-sleeved vest with white trim, cuffed at the forearms, paired with puffy olive-green sleeves at the biceps and a wide collar. A handgun holster attaches to his left side.

Personality-wise, Satomi exhibits intense admiration for specific individuals, declaring himself a "Ninomiya zealot" for Masataka Ninomiya. He also idolizes Takuma Yuba, insisting Yuba could defeat anyone in single combat.

Within Kusakabe Squad, he interacts with Shun Midorikawa—who introduced him to Yūma Kuga and Osamu Mikumo—and operates under Squad Leader Saki Kusakabe. His combat role centers on gunnery during Border operations. After returning from a business mission, he advised Osamu Mikumo on tactics against Yuba Squad and Ninomiya Squad prior to Rank Wars.

Notable trivia includes his fondness for exercise, his teammates, Ninomiya, and fried oysters. His pragmatic combat philosophy surfaces in the quote: "Just 'cause you know what's coming doesn't mean you can stop it," reflecting his belief in Ninomiya's overwhelming skill.