Nene Todoroki begins as a first-year student at Ousai Academy and advances to her second year. She leads the Robot Research Club, a little-known organization within the school. Academically, she ranks fifth among her peers. Her passion lies in inventing and repairing mechanical devices, from everyday electronics like clocks to complex creations such as a lifelike robot dog, showcasing notable technical skill in robotics and machinery.

Her personality blends helpfulness and kindness, often aiding others with mechanical repairs. However, she displays a marked preoccupation with sexual themes, particularly through her fascination with developing mechanical sex toys. This trait defines her character: she frequently wears self-made vibrating devices during school hours and occasionally forgets to deactivate them. She discusses these inventions openly with peers like Suzu Hagimura and Takatoshi Tsuda without embarrassment. Her creations include specialized items such as a Medusa-inspired hairpiece with functional snake components and compact vibrators designed for smaller individuals.

Suzu Hagimura stands as her closest friend, with interactions including sleepover invitations and familiarity with Suzu's family. Though Suzu declines offers to use her inventions, Nene demonstrates genuine care through practical gestures like crafting a custom-sized desk for Suzu's height. She maintains civil interactions with others, including Mutsumi Mitsuba and Takatoshi Tsuda, though Takatoshi expresses discomfort regarding her open discussions and use of sexual devices at school. She offers Takatoshi Valentine’s Day chocolates, indicating friendship.

Beyond club duties, she assists in the school library, suggesting potential Library Club involvement. During the anime's second season, she hosts an educational segment titled "Nene Todoroki's Trivia," focusing on historical sexual aids. These segments often require Suzu and Takatoshi to intervene when her enthusiasm leads to overly explicit content. She persistently attempts to share or promote her inventions with peers throughout the series, though these offers are consistently declined.

Her core traits—technical ingenuity and overt preoccupation with sexual machinery—remain consistent across official media, with minimal character development. Her role primarily involves recurring comedic interactions centered on her inventions and their unintended disruptions within the school environment.