Natsumi Murakami is the twenty-eighth student in Class 3-A at Mahora Academy, with a birthday of October 21. She has short pink hair, green eyes, and in the manga, freckles. She describes herself as an ordinary middle schooler with no unique talents or magical abilities. Her personality is shy and sweet, and she loves acting, but she is deeply insecure about her own appearance, feeling that her body is not mature-looking. She dislikes her ad-libs and her unmanageable hair, and in the manga she has a complex about her freckles. She is a member of the school's drama club, and it is possible that she has exceptional acting ability, though her low self-esteem prevents her from fully recognizing it.

Her primary motivation is to improve as an actress and to overcome her insecurities. She often wishes she could be more confident. In the story, she serves as a supporting character and is part of the group of students who smuggle themselves into the magical world out of concern for Negi. She is one of very few classmates who have no romantic tension with Negi and no magical abilities, making her a more grounded presence.

Key relationships include her roommates Ayaka Yukihiro and Chizuru Naba, with whom she shares a dormitory. When Kotaro Inugami begins staying with them, Chizuru forces the idea that Kotaro is Natsumi's younger brother, and Natsumi adapts to the role surprisingly well. She grows into a caring older sister figure over time. Her development is shown through her increasing willingness to take on acting roles and her gradual acceptance of her own appearance, though she remains shy.

Natsumi's only notable ability is her acting talent, the true extent of which is unknown because she rarely showcases it due to her lack of confidence. She has no magical powers or combat skills in the main Negima storyline.