Ichabod Crane est "ressuscité" et se retrouve deux siècles et demi plus tard dans la ville de Sleepy Hollow d'aujourd'hui. Alors qu'il doit s'adapter à une réalité moderne encore inconnue pour lui, il tente d'élucider le mystère du cavalier sans tête. Mais Ichabod est loin de se douter qu'il n'est qu'aux balbutiements d'une longue aventure, que le meurtrier sans tête est le premier de quatre cavaliers de l'Apocalypse et l'un des nombreux ennemis auxquels il devra faire face pour protéger Sleepy Hollow... ainsi que le monde entier.
65 million years ago, the knights of the Ryusoul Tribe were selected to participate in a war campaign against the dictating Druidon Tribe who sought to rule Earth. But the Druidon's war campaign was halted by the meteor that brought the age of the dinosaurs to an end, forcing them to flee into space. Meanwhile, the Kishiryu were placed in a deep sleep as a failsafe should the Druidon return. The chosen knights choose to live in peace while passing their mantle down across generations. In the present day, the Druidon return to reclaim Earth as the current generation of knights, the Ryusoulgers, battle them with the support of Ui Tatsui and her father Naohisa Tatsui.
When a group of archaeologists uncover the tomb of a legendary warrior, they unearth Kuuga’s belt, accidentally releasing an ancient race of monsters called the Grongi, bent on destroying humanity. Enter Yusuke Godai, a modern-day guy next door, who learns he is telepathically linked to the mysterious stone belt. With its power, he transforms into the legendary warrior known as Kuuga, humanity’s only defense against the murderous Grongi monsters.