Natsumi is the fourteen-year-old granddaughter of Hakase, the inventor who created the Pipo Helmet technology. She lives with her grandfather in his laboratory and serves as a key member of the team working to capture the mischievous monkeys and thwart Specter's plans. Her personality is bright and cheerful, often exhibiting a victorious and confident attitude. She can be bossy at times, especially toward Kakeru, whom she frequently treats like a younger brother, but she also shows a softer, more affectionate side, particularly after Hiroki saves her life in an episode of the second season. Natsumi's primary motivation is to support her grandfather and friends in their mission, and she acts as the laboratory operator, coordinating monkey-catching operations and providing assistance from the base. Despite her competence in many areas, she has a notable weakness for cooking; her attempts in the kitchen are so disastrous that they have made Hakase and Kakeru ill. Her most personal connection is to her pet monkey Kuuta, who is eventually revealed to be Specter, the main antagonist, adding an emotional layer to her involvement in the conflict. Over the course of the series, Natsumi demonstrates loyalty, courage, and a growing bond with her teammates, especially Hiroki, and her role evolves from a purely supportive position to one where she occasionally participates directly in field missions.