Kurumi Nishina features in the Doukyuusei franchise as the girlfriend of Kazuya, the protagonist's close friend. She sports orange hair in long twin braids secured with a ribbon hair tie, brown tareme eyes, and a slim physique, standing 155-156 cm tall with bust-waist-hip measurements fluctuating between 80-56-81 cm and 83-56-84 cm across depictions. Her standard attire consists of a sailor school uniform: a blouse, pinafore dress, and dress shoes.

Kind, naive, and docile by nature, she occasionally refers to herself in the third person. Raised under an overprotective father's strict supervision, she internalized a belief that romantic relationships must remain "pure," causing friction with Kazuya over differing expectations of physical intimacy. This tension drives her to seek the protagonist's perspective on her relationship struggles, positioning her within a love triangle through these interactions.