Femina Novum is an 18-year-old British Adapter, the first known of her kind. She possesses pink eyes and shoulder-length blue hair, along with a facial mark and a distinctive collar. Her unique ability, the "Harmony" Allergy, sets her apart from other Adapters. This power necessitates her indefinite confinement within a protective capsule; release would prove fatal. Despite this physical isolation, she communicates telepathically.

She created the song "Umidorika," which becomes a vital emotional link connecting the main characters Amuri, Suzu, and Perrier, who each discover others know the song they thought was uniquely theirs. During the crisis of the junk planet Galapagos hurtling towards Earth, Femina contacts the protagonists telepathically. She guides them to fully accept their Allergies, enabling them to amplify their abilities through their Stora suits, unifying their efforts.

Her Harmony ability directly resolves the conflict. She instructs the group on using this power collectively, transforming Galapagos into a "shiny pure white" state capable of absorbing all projectile attacks, halting the plan to destroy Earth's atmosphere. Her telepathic support continues as the protagonists redirect Galapagos back into space, neutralizing the threat. Her actions facilitate Perrier's reconciliation with her alternate persona Vernier and enable Ukatan's reprogramming away from antagonist control. Following the crisis, she remains confined within her capsule, her physical freedom impossible due to the fatal risk of her Harmony allergy.