OVA
Description
Natsumi Koshigaya is a main character and a first-year middle school student at the Asahigaoka Branch School. She is thirteen years old, has a birth date of January 24, stands 155 centimeters tall, and has blood type B. She is the youngest daughter of Yukiko Koshigaya and the younger sister of both Komari and Suguru.

Natsumi is best known for her fun-loving, carefree, and mischievous personality. She enjoys playing pranks on her friends and family, often with a cheeky attitude, and tends to be rebellious toward authority figures, especially her mother. Natsumi does poorly in school because she prefers to be lazy rather than study, and she often tries to get out of trouble by pinning the blame on someone or something else. Despite these flaws, she is incredibly creative and resourceful, frequently coming up with ideas for group activities and adventures. Her boundless energy makes it hard for her to sit still, and her playful, cheerful nature brings a great deal of comedy to the series. She also has a more tomboyish side, being very outdoorsy and disliking girly clothes. A notable part of her past is that she used to have a brother complex, once claiming she wanted to marry her older brother Suguru, a fact she now finds very embarrassing.

Her primary motivation is the pursuit of enjoyment and fun, seeking out adventure and excitement in the peaceful, rural setting of Asahigaoka. She is the member of the group who most often devises schemes and activities to keep everyone entertained.

Natsumi's role in the story is to be the primary source of comedic relief and energetic chaos, providing a lively contrast to the calm and quiet countryside. She is also the main focal character in the film Non Non Biyori Vacation.

Her key relationships are central to her character. With her older sister Komari, Natsumi constantly teases her about her short height and immature personality, yet underneath the rivalry, there is a deep, genuine sisterly affection. She also has a special bond with the younger girl Renge Miyauchi, as Natsumi's straightforward personality complements Renge's curious nature. She is one of the few people who understand Renge and takes her questions seriously. With Hotaru Ichijou, a transfer student from the city, Natsumi becomes a good friend who introduces her to the fun side of country life. Her relationship with her mother Yukiko is defined by frequent clashes over chores and grades, though there are moments that show Natsumi's underlying care for her family. She also looks up to Hikage Miyauchi as a kind of older sister figure.

Over the course of the series, Natsumi experiences gradual personal growth. While she begins as a self-centered troublemaker, her interactions with her friends and family, especially her willingness to engage in community activities, show a developing appreciation for her surroundings and the bonds she shares with others. She learns more about the importance of responsibility and the value of her relationships, though she never loses her core personality.

Natsumi does not possess any supernatural or combat abilities. Her notable traits are her cleverness, creativity, and social agility, which she uses to execute pranks and navigate tricky situations.