Kuri Sugimoto, one of Yasuko Sugimoto's three older sisters and a fellow Fujigaya Girls' Academy alumna, possesses a cynical and blunt personality. She regularly clashes with Yasuko to establish boundaries and counter her younger sister's selfish tendencies, yet maintains a fundamentally helpful nature. Like Yasuko, Kuri garnered significant admiration and popularity at Fujigaya, though she remained indifferent to the attention.

Kuri harbored silent, unrequited romantic feelings for Masanori Kagami, a Fujigaya teacher, mirroring Yasuko's later infatuation. She is frequently depicted smoking, often shown with a cigarette.

Her interactions reveal protective instincts. Upon learning of Yasuko's relationship with Fumi Manjōme, Kuri confronted Fumi directly, warning her about Yasuko's potential to cause emotional harm—implicitly referencing Yasuko's history of unstable attachments. Kuri occasionally joins family teasing directed at Yasuko, particularly regarding her romantic inclinations and perceived fickleness.

Physically, Kuri has grayish-dark hair, purple eyes, and stands 1.70 meters tall. Her narrative function primarily challenges Yasuko's behavior and offers cautionary perspectives on relationships within the familial dynamics.