真壁一骑是个生长在对日本而言十分乡下的龙宫岛上的少年──对他来说,像这样的和平是普通到不能在普通的状况。 但当由硅所构成的不明生物·异界体(Festum)开始攻击龙宫岛时,他才开始注意到他现在所拥有的和平生活不过只是个被创造出来的假象。 为了取回自己的和平生活,他和同伴开始一起搭乘人类所创造出来的巨大兵器·法夫那(Fafner)和异界体战斗── 在激战的彼端,等待着他的是……The youth of Tatsumiya Island believed that they had ordinary lives... until the advent of the Festum, extraterrestrial intelligent life forms intent on assimilating all humans. Abruptly, their once peaceful island transforms into a high-tech military fortress to counter-attack the hostile aliens. Their shock intensifies when they learn that only they can pilot the Fafner, a class of humanoid-type robots that represent the final and only weapon against the Festums and their divine powers.