Eto, a future incarnation of Kakeru—son of the legendary hero Takeru—is imprisoned by the demonic ruler Lucifon after failing to save his allies and lover, Natasha. Tortured for years and haunted by visions of her death, he is thrust back in time by Marlene, a former ally, using a mystical artifact tied to Lucifon. To avoid disrupting the timeline, he adopts the alias "Eto," concealing his identity behind a helmet while covertly uniting rebels against Lucifon’s forces, which spread a petrifying black mist.

Armed with foreknowledge of events, Eto maneuvers allies like Marlene and Natasha through calculated guidance, withholding truths of their fates to stave off despair. He leads with a focus on collective strength over hierarchy, wielding a sword that channels wind-based attacks and tactics sharpened by reliving past battles. Yet his resolve strains under Marlene’s hidden agenda and the emotional toll of confronting tragedies he vows to prevent. A critical rule binds him: revealing his identity to his younger self would instantly return him to his doomed timeline.

Eto’s journey pivots on balancing guilt from past failures against the imperative to rewrite history. His interactions with Natasha and Marlene expose buried loyalties and suppressed emotions, particularly when personal bonds conflict with strategic demands. Success hinges on dismantling Lucifon’s reign, preventing his allies’ destruction, and forging a future where Natasha survives—a redemption etched in risk and sacrifice.