In a futuristic setting, a new type of shock-absorbing cardboard revolutionizes global trade in 2046. This innovative material becomes the arena for a beloved children's pastime known as 'LBX' (Little Battler eXperience). Yamano Ban, a young enthusiast of LBX despite lacking his own mecha, receives a mysterious package from a stranger four years later. Inside the case lies the model AX-00, along with a cryptic message that he now carries the weight of humanity's dreams and struggles.