For thousands of years, people lived in a status quo maintained by the brave knights who defended the borders of human realms from the demonic scourge. But a new demon king had arisen. He united the warring demon princes and launched an invasion of an unprecedented scale that obliterated one human bastion after another. Facing annihilation, humanity pinned their last hopes on a ritual discovered in an ancient scroll. It described how to summon brave heroes from another world to help them resist the demonic menace. A group of eight teenagers will now have to bear the heavy mantle of a hero. Only by trusting in their teachers and each other will they be able to succeed.