Danball Senki

In 2046, a new type of reinforced cardboard capable of absorbing 80% of impact is developed, leading to a shift in global trade. This material becomes central to a children's hobby known as LBX. Four years later, a boy named Yamano Ban, who enjoys LBX but lacks his own mecha, receives a case containing the model AX-00 from an unknown woman. She informs him that he now carries the hopes and despair of humanity.