Nagisa Momoe transformed into the witch Charlotte after drowning in despair. Her wish, revealed in Magia Record, was for "one single cheesecake which my mom will think is the best," driven by a desire to earn affection from her terminally ill mother. This stemmed from a tragic family situation where her mother resented her, viewing Nagisa as the cause of problems due to an absent father. Her mother died without tasting the cheesecake, leaving the contract unfulfilled and deepening Nagisa's despair.

As Charlotte, she notoriously defeated Mami Tomoe in the original timeline. Following Madoka Kaname's universe-altering wish, Nagisa became part of the Law of Cycles, erasing all witches. In *Rebellion*, she returned as an emissary of the Law of Cycles alongside Sayaka Miki, tasked with helping Madoka rescue Homura Akemi. Nagisa entered Homura's barrier disguised as her witch form under the alias "Bebe." She resided with Mami Tomoe, who believed Bebe was her oldest friend due to the barrier's memory effects. Nagisa maintained this disguise while fighting Nightmares, retaining her own memories.

Her personality blends childish exuberance with perceptiveness, often providing comic relief while speaking eloquently. As Bebe, she displayed heightened childishness, including panic at the thought of turning into cheese. She shares a close, mother-daughter-like bond with Mami, which endured even after Nagisa revealed her true identity and apologized. Her stated motivation for joining the *Rebellion* mission was a desire to eat cheese again.

She wields a trumpet-shaped horn firing explosive bubbles capable of cracking witch barriers, demonstrated against Homulilly. This weapon embodies magic enhancing self-assertiveness and greed, stemming from regret over her limited wish. As an agent of the Law of Cycles, she gained the ability to shift between human and witch forms and summon familiars like Pyotr and Polina. Her transformation incantation is "Parmigiano Reggiano!", reflecting her cheese obsession.

After Homura Akemi rewrote reality at the end of *Rebellion*, Nagisa was separated from the Law of Cycles and reverted to an ordinary human child. Depicted in civilian attire with no magical girl memories, she integrated into normal life, implied to attend school. A final scene hints at a renewed connection with Mami, who saves her from falling cheese packages.

In *Magia Record*, multiple Nagisa iterations appear. One stems from a timeline where Madoka's wish directly saved her from becoming Charlotte. Another explores an alternate backstory elaborating her wish-granting process and relationship with her mother, reinforcing the original contract's tragedy. These variants highlight her role as a Law of Cycles messenger in Kamihama City, with her cheese fixation remaining consistent.