Kasumi Honjou attends Marehoshi Private School's Takao Branch as a second-year student. She presents a cool appearance with outstanding proportions, favoring a mature fashion style distinct from her peers. Her wardrobe features studded belts, wrist accessories, necklaces, and textured tops. Her original performance outfit includes black tights, silver pumps, fluffy anklets, and grey-black themed hair accessories, with later costumes incorporating a miniature top hat and a tie. She possesses shoulder-length indigo hair with layered, messy bangs and sharp cerulean eyes.

Kasumi once aspired to be an idol but set that dream aside upon entering junior high school, becoming the ace of the Survival Game Club instead. She speaks using the masculine pronoun "boku" and relatively masculine language. Kae Hiiragi nicknames her "Angel," while Kasumi calls Kae "Princess."

Her background includes creating a techno-idol persona before retiring from idol activities to focus on survival games. She initially resisted joining the Lyrical Tradition Dance Club, demanding a survival game challenge as a condition for membership. After losing the challenge, she agreed to join, reactivating her dormant passion for performing.

As a member of the idol unit KiRaRe, she competes in the Prism Stage. Her character development involves confronting personal doubts during the group's preparation for the finals, especially when statistical analysis showed minimal chances against the top-ranked group Stellamaris. Despite this, she committed fully to KiRaRe's collaborative effort to redefine their approach and challenge the frontrunners.

Her musical contributions extend beyond the anime series, encompassing duet tracks like "Gadget wa Princess/Sēno de Tobe tte Itten no!" with Kae Hiiragi and later group singles such as "Sin City," featuring Mikuru Bandou and Ruka Ichijou.