The hope of humanity. The savior destined to rescue a world on the brink of destruction by the Demon King. There was a girl known as the “Hero.” She fought diligently to save humanity, defeated the Four Heavenly Kings of the Demon King’s army, and was on the verge of slaying the Demon King himself. However, in the final battle, the Hero was defeated by the Demon King, plunging humanity back into the abyss. In a certain rural village lived a boy named “Allan,” who was the childhood friend of the girl hailed as the Hero. Vowing revenge against the Demon King who took his precious childhood friend, Allan, despite having no special talents, honed an extraordinary sword technique through sheer effort, and finally avenges her by clashing blades with the Demon King, who had been severely injured in the battle with the Hero. However, even after avenging her, she does not return. Consumed by sorrow and loss, Alan loses his life. . . . . .and finds himself back in time, before his childhood friend was taken to the battlefield as the Hero. Having witnessed a future of despair, Alan vows. With the power he gained for the sake of revenge, this time, he will protect his dear childhood friend until the end.