Kurumi Nishina is an 18-year-old high school student featured in the visual novel and OVA "Doukyuusei: End of Summer." She possesses brown eyes and hair that varies between brown or orange across adaptations, typically styled in long twin braids reaching her waist or chest. Her attire is a school uniform, frequently consisting of a blouse, pinafore dress, and hair accessories like ribbons or ties.

Raised by an overprotective father, Kurumi emphasizes relationships she deems "pure," explicitly avoiding physical intimacy. This belief causes significant tension with her boyfriend, Kazuya, who holds different expectations for their relationship. Seeking understanding, she turns to the protagonist for advice on a male perspective regarding these struggles.

Kurumi exhibits a docile, kind, and naive personality, often referring to herself in the third person. Her gentle demeanor is evident in interactions, though her strict adherence to idealized romance complicates her dynamic with Kazuya. Physically, she has a slim build, pale complexion, and freckles. Her height is 155–156 cm, with measurements consistent with a petite frame.