Nouvelle Tokio City locates on the place where it used to be Tokyo Bay. At the first glance, the prosperous city seems to enjoy its freedom and peace, but the city is suffering from the crimes.

Senmuji Maito is a perfect 15-year-old boy, bright, handsome, smart, and all-around sportsman. Furthermore, he is the leader of Senpuji Trading group, and a multimillionaire. He spends his private fortune to found "Brave Express Squad" which consists of several robots. They are the robots that have various special abilities. Above all, the leader, Gaine, has a super artificial intelligence and has own personality. They can transform into trains. In case of incidents, they will appear anywhere in the world using the highly developed railway system.