Natsumi Onitsuka is a first-year student at Yuigaoka Girls' High School who joins the school idol group Liella! as a second-generation member during the second season. Before becoming a school idol, she was a small-scale L-Tuber running her own channel called Oninatsu, where she referred to herself as the CEO. Her driving motivation is a strong belief that money makes the world go round, and she initially approaches Liella! with the sole intention of leveraging their growing popularity to increase her online following and earn ad revenue. Natsumi is generally friendly and approachable in demeanor, but she can be manipulative, selfish, and willing to do whatever it takes to achieve her financial goals. She has a keen eye for fashion and often tries to control situations from behind the scenes. Her childhood was marked by attempts to break into various entertainment fields, but her focus was always on monetary gain rather than passion. After suffering losses in the stock market, she takes on multiple part-time jobs, including delivering for Lber Eats and working for a moving company called Sunshine Moving. She also becomes the producer for Liella!, uploading vlogs of the group's daily lives to attract more viewers and generate income. Over time, however, her genuine involvement with the group begins to change her perspective. A weekend trip to the Sakurakoji family cabin in Hokkaido helps her appreciate the charm of school idols for reasons beyond money, marking a key development in her character. Natsumi has a younger sister named Tomari Onitsuka, whom she frequently praises and supports. She has a distinctive speech pattern, often ending her sentences with the phrase desu no, and her catchphrase is OniNatsu! Physically, she has a slim figure, blonde to pink ombré hair styled in front twin braids with small bows, and a white flower above her right ear. Her eyes are hot pink, and her image color is hot pink. As an L-Tuber and aspiring influencer, she is always looking for new ways to earn money, but her time with Liella! slowly reveals a more sincere side to her personality. She is also a member of the sub-unit 5yncri5e.