I've Been in Charge of Being the Savior on a Rotational Basis, But This Time It Seems I'm the Demon King.

The Savior. A hero destined to defeat the Demon King, yet such a figure has never once truly appeared in the world, existing only as a legend. Six chosen individuals serve as Saviors every cycle, facing the Demon King again and again. Each time they challenge him, they are brutally slain, only to be reborn and forced to fight once more. The cycle has repeated so many times that they can no longer remember how often they have died. Everyone believed this endless struggle was simply their fate until this cycle proved different. One of the six Saviors, Rudbeckia, has been reborn not as a hero, but as the next Demon King. Thrown into an impossible existence, the former Savior struggles to survive while searching for a way to reunite with his companions. Yet as he begins to uncover the hidden truth behind their repeating fate, the future waiting beyond that revelation may change everything…