Enter Kuros, an average high school student who gets sent into another world after getting into a car accident. Losing his memory and forgetting his name, he became known as the Cross Sword hero. In search of a way to open up the Cross Gate to return his own world, Kuros and one of three heroines partner up to travel across the world of Etatia in search of clues. Meanwhile, a mysterious cloaked figure seems intent on disrupting their journey of getting Kuros back to his own world...

很久很久以前，一位传说中的王者统一了ラグノア大陸。不过，在王者死后，大陆陷入多次的战乱之中呃分裂成6个国家。在这时候，魔王军突然出现。魔族的大军向各个郭嘉发动了进攻，在短时间内就把大陆的大半收入自己的版图。劫后余生的各国公主们，投靠到了受害较浅的ラウディア国。另一方面，收到魔王军侵略来临的ラウディア国王在深思熟虑之后，向他的三位王子下达了各自的使命。 然后，作为ラウディア第3王子的主人公即将投身到战争的浪潮里去……