Kamen Rider Agito: Project G4 (2001)

A large group of Unknowns come to a military facility, drawn by the powers of children who are being experimented there. Two children, Sayaka and Rei, manage to escape and bump into Shouichi and Ryou. At the police headquarters, Ozawa and Hikawa are joined by a trainee who poses in order to steal Ozawa's blueprint of G4, a much stronger battle unit than G3-X and even Agito. Can Agito, Gills, and G3-X protect the children and settle things with G4 at the same time?