Momoka Kurumi, the 17-year-old older sister of Kurumi Erika, is a supporting character and second-year student at Myoudou Gakuen High School. She works as a popular professional fashion model, appearing in magazines, a career both sisters dreamed of pursuing since childhood inspired by their mother, a former model. Her demanding modeling schedule causes frequent school absences, fostering social isolation; classmates view her as an unapproachable "star," hindering ordinary friendships. Her only school connection is Tsukikage Yuri, who provides class notes during absences and shares lunch breaks. Their bond strengthens when Momoka invites Yuri to Paris and collaborates on a modeling project.

Exuding a calm, mature demeanor and understanding individual differences, Momoka enjoys fashion and modeling partly to promote designers by popularizing their clothing. Despite her professional success, she envies Erika's normal life, friendships, and participation in activities like the Fashion Club. This envy contrasts sharply with Erika's resentment of Momoka's popularity, straining their sibling dynamic. Momoka typically responds to Erika's hostility with patient support, though her gestures are often misinterpreted as teasing.

A pivotal moment arises when Momoka's suppressed jealousy and frustration cause her Heart Flower—a dahlia symbolizing splendor and elegance—to wilt. This attracts the Desert Apostle Kumojaki, who transforms her makeup set into a Desertrian. As the monster, Momoka vents resentment over her isolation and longing for Erika's ordinary experiences. During the battle, Erika (as Cure Marine) hesitates, recognizing her role in Momoka's pain. Encouraged by Cure Blossom, Cure Marine defeats the Desertrian. Momoka and Erika then reconcile by openly admitting their mutual envy: Erika admires Momoka's success, while Momoka covets Erika's friendships and normalcy. This confrontation establishes a healthier, more familiar relationship where they comfortably tease each other.

Momoka continues supporting Erika's interests, facilitating the Fashion Club's visit to her photoshoot and providing feedback on Erika's designs. Her modeling career remains active, demonstrated by her collaboration with Hanasaki Tsubomi for a magazine shoot after another model's unexpected withdrawal.