Natsumi Oohashi is a supporting character in the series More Than a Married Couple, But Not Lovers. She is a high school student and a close friend of Akari Watanabe, belonging to the same cheerful gyaru group as Sachi Takamiya. Natsumi has long maroon hair and red eyes, and the anime portrays her with a distinctive cat-like mouth. She is slightly shorter than Akari.

Personality-wise, Natsumi is sweet, extroverted, and bubbly. She often has a smile on her face and enjoys spending time with her friends doing fun activities, such as visiting cafés to try popular dishes or going to karaoke. Her upbeat and friendly nature makes her a warm presence in the group.

Her primary motivation is maintaining her friendships and supporting her friends in their daily lives and romantic endeavors. She does not have a major personal goal driving the plot; instead, she appears as a reliable companion who encourages and gossips with Akari and Sachi.

In the story, Natsumi’s role is that of a confidante and source of lightheartedness. She provides social context outside of the main couples’ training program and offers a relatable perspective as a typical high school girl navigating relationships. Her key relationships include her friendship with Akari and Sachi, as well as her boyfriend Ryo, who attends a different school. This relationship is mentioned but not deeply explored, serving to highlight that Natsumi, unlike the main characters, has a straightforward romantic situation.

Natsumi does not undergo significant personal development over the course of the series; she remains a consistent, cheerful figure. She has no special abilities or skills beyond being an attentive friend and a sociable person. Her notable traits are her loyal friendship and her ability to bring levity to scenes.