Age: 12

Eri Ninamori is Naota's classmate. In the series, she is referred to as "Ninamori," her last name. She is the daughter of the mayor of Mabase and is class president. Ninamori has N.O. powers as well: Naota's third robot, which appears at first as "cat ears" transfers to her instantly in the 3rd episode, while the two of them are fighting, as the Medical Factory's siren blows. She projects a proper, even slightly stuck-up personality, and conceals personal information to an almost obsessive degree; she does not even let her classmates know that she needs corrective lenses, instead wearing contacts while at school. Even with her class president status, however, Eri isn't above breaking the rules to get what she wants. She rigs the voting during the casting for the school play in order to get the lead role and have Naota cast opposite her, which (along with letting him see her wearing glasses) hints at her crush on Naota. Other hints are her expressed dislike of Mamimi and a final scene with Naota by a vending machine that mirrors Mamimi and Naota's early-series interactions. Ninamori is highly intelligent, if a little jaded. Much like Naota, Ninamori attempts to act mature, and although her parents' problems trouble her deeply, she refuses to admit it until near the end of the series.