Lilyu and his best friend Joey are on an expedition as part of the boy soldier unit of the Highland Kingdom. On their last night before they can return to their hometown of Caro, where their childhood friend Nanami awaits them, they are ambushed by the enemy in the mountains. Cornered by the soldiers, the two promise to meet again and jump into a waterfall at night.When Lilyu awoke from unconsciousness, he found himself inside a mercenary fort of the enemy City Alliance army. Working as a prisoner in the fort, doubts about the Highland army began to grow within Lilyu. Had they been framed? If so, who was behind it...?Joey then appears before Riryu. Joey, too, had drifted ashore in enemy territory.To find all the answers, Lilyu and Joey vow to return to the town of Caro and escape the fortress. But an even larger conspiracy awaits them...