Yachiyo Hinata is a first-year student at Stella Women's Academy and the granddaughter of its chairman. Standing at 145 cm, she is the shortest member of the C³ Club and goes by the nicknames "Hachi" or "Ha-chan" among her peers. She possesses ochre-colored hair cut to neck length, featuring a distinctive, expressively moving ahoge, and matching brown eyes. Her combat gear includes orange eye protection and gloves that complement her hair and eye color.

Specializing in long-range combat as a sniper, her primary weapon is a 1.23-meter-long Tokyo Marui replica of the Accuracy International Arctic Warfare Suppressed (AWS), creating a notable contrast with her small stature. When sniper rifles are unsuitable, she utilizes a Tokyo Marui Type 89-F assault rifle, with a WE P228 pistol as her sidearm. Her combat style prioritizes pragmatism and psychological tactics. She once left her ghillie suit visible as a decoy while attacking from an unexpected position wearing a fairy costume during a match against Aoi Seto. She employed similarly unconventional methods to unsettle opponents in the "Field Queen Contest."

Personality-wise, Yachiyo exhibits energetic and sometimes childish traits, fitting a "spoiled child" dynamic within the club. She is sensitive about her physical appearance, particularly her height and chest size, leading to jealousy of taller club member Rento Kirishima's physique. Audience comments about her age and height during the Field Queen Contest visibly agitated her, aligning with assertive behavior compensating for stature. Her surname "Hinata" means "sunny place," while her given name "Yachiyo" combines the characters for "eight," "thousand," and "generation." The surname follows a vehicular naming theme derived from the Japanese battleship Hyūga, using the alternative reading "Hinata." Her documented role remains consistent as a supportive club member providing comic relief through her energetic personality and reactions to her physical stature.