Natsuki Aizawa is a 15-year-old student sharing Class 1-B with Yuushin Hirose and Hiyori Nishiyama. Standing 167 cm tall, she sports short orange hair, a style adopted after middle school heartbreak. She had initially grown her hair out due to a crush on her homeroom teacher, only to cut it short upon discovering he was married, resolving to grow it again only for someone she truly loves. Her birthday falls on July 8. Exuding a cheerful, happy-go-lucky energy, Natsuki possesses an explosive temper, frequently reacting with physical force towards Yuushin's inappropriate remarks. Despite her tomboyish exterior, she harbors a deep fondness for small, cute things, finding Hiyori exceptionally adorable. This affection drives her to fiercely protect Hiyori and actively champion her relationship with Yuushin, even shedding tears of joy when they start dating. She serves as one of Hiyori's close confidantes, alongside Ritsuka Nakano. Natsuki enjoys notable popularity among female classmates, sometimes surpassing the boys, and occasionally receives gifts like Valentine's chocolates from unfamiliar girls. Her tomboyish traits often lead others to perceive or treat her as a boy. She shares a long-standing friendship with Yuushin, having been classmates since middle school, though she readily threatens him whenever he upsets Hiyori. Her development includes taking a part-time job at a convenience store, where an older boy named Kanata becomes a frequent visitor. With indirect help from Hiyori and Yuushin, Kanata eventually asks her out, marking the beginning of their romantic relationship.