Natsumi Ohashi is a supporting character in the series. She is a third-year student at Seishun Academy and belongs to a group of cheerful gyaru friends alongside Sachi Takamiya, with Akari Watanabe as a close friend. Natsumi is known for her outgoing and bubbly personality, often wearing a smile and enjoying social activities such as visiting cafés to try new dishes and singing karaoke. She refers to herself in the third person, adding to her lighthearted demeanor.

In terms of background, she has a boyfriend named Ryo who attends a different school, though this relationship is not deeply explored in the story. Her primary role is that of a supportive friend to Akari, and she occasionally helps foster the connection between Akari and her partner Jiro Yakuin during key moments. She maintains neutral terms with the male friend Shū but becomes visibly annoyed by his persistent focus on Akari, especially when it interferes with group activities such as a summer job at a beach café.

Natsumi does not undergo significant personal development over the course of the narrative; her character remains consistently cheerful and dependable. She does not possess any special abilities beyond her social charm and her tendency to act as a catalyst for the main couple's interactions. Her physical appearance includes long maroon hair, red eyes, and a distinctive cat-like mouth in the anime adaptation.