Ragna Crimson follows a world where humanity survives under the constant threat of ancient dragons, creatures so powerful that only two methods can reliably kill them: freezing their blood with silverine, an aura drawn from silver weapons, or burning their bodies away with sunlight.
In that brutal age, Leonica, a gifted young hunter, travels with her close friend Ragna. He is widely feared as cursed, because dragons always seem to appear to attack him and slaughter the people closest to him, yet Leonica believes he still has potential and chooses to fight at his side. Ragna, in turn, trusts that Leonica's overwhelming strength may be enough to shield her from the misfortune that follows him.
That fragile hope collapses when Ragna dreams of Leonica's death and comes to believe it is a prophecy. On the day he fears is coming, he meets his future self, who grants him immense power and memories from the future so he can protect Leonica. Armed with that second chance, Ragna joins forces with the mysterious Crimson and throws himself into a relentless war to wipe out the dragons for good. The series turns that desperate vow into a harsh campaign of survival, revenge, and impossible odds.