Nouvelle Tokio City occupies the site where Tokyo Bay once lay. At first glance the prosperous metropolis appears to enjoy freedom and peace, yet it is plagued by crime. Senmuji Maito, a flawless 15‑year‑old boy, bright, handsome, intelligent, and a versatile athlete, serves as the leader of the Senpuji Trading Group and is a multimillionaire. He uses his personal fortune to establish the Brave Express Squad, a team of robots with diverse special abilities. Their leader, Gaine, possesses a super artificial intelligence and an independent personality. The robots can transform into trains and can appear anywhere in the world during emergencies, using a highly developed system.