There has been much conflict between the races of the 'Humas', the 'Gabranth', and the 'Evila'. To combat the 'Evila' race's Demon King, the kingdom summons five high school students from 21st century Japan who have the power of Heroes. However, only four out of five of those students had the status title of 'Hero'. Okamura Hiiro was summoned by accident since he sat near the other four students in class. Unlike them, he did not have the title of a 'Hero' but instead he had the title of 'Word Master' and 'Innocent Bystander'. Seeing through the 'Humas' kingdom's deceit and insanity, Hiiro decides that he has no wish to partake in their selfish war. Leaving the castle, Hiiro decides to join the Adventurer's Guild and does whatever he feels like. Who knows? Maybe there is some merit to being a 'Word Master' and an 'Innocent Bystander'.

In the latter half of 21st century, humans leave the Earth and begin to live in space. In order to adapt to the environment in space and deal with the hostile aliens in Jupiter, genetically engineered children called "Princes" are artificially raised and trained to be pilots of armed robots "AHSMB (Advanced High Standard Multipurpose Battle Device). This is a story about one of the teenage "Princes," Hitachi O Izuru, who studies in an academic city Grandzehle.