Natsumi, granddaughter to the genius inventor known as the Professor, operates critical laboratory equipment supporting missions to capture escaped monkeys wreaking global chaos. She serves as a key field operator during these efforts. Her personality shines with victory and cheer, often engaging the energetic elementary school student Kakeru in a somewhat childlike manner.

She was once the owner of a small white monkey named Kuuta before his disappearance. Kuuta became the vessel for the entity Specter after being tricked into wearing a Pipo Helmet, transforming him into an intelligent antagonist commanding other monkeys. This event fuels Natsumi's personal stake in the conflict against Specter.

Appearing again in the second season, Natsumi continues her vital operational support role. A significant race event during that season shows her reacting directly to sudden cannon fire from a Tank Saru Machine alongside Hiroki, demonstrating her involvement in field incidents beyond the lab. Her interactions with Hiroki, Kakeru's courteous classmate, reveal his very blatant crush on her, adding a relational dynamic.

Her background remains anchored to the laboratory team and her profound connection to Kuuta/Specter. She provides consistent operational support across both seasons using her skills. The resolution of Specter's storyline sees him ultimately revert to his original form as Kuuta, restoring Natsumi's bond with her pet monkey. Her role is consistently defined through her laboratory duties, her relationships with the Professor and Kuuta, and her interactions within the core team.