Allen, the eldest son of a once-prestigious noble house, makes a devastating discovery: his beloved brother Julius Reinhart has been possessed by an otherworldly force. As his family remains willfully blind to the imposter dwelling among them, Allen discovers an extraordinary power—the ability to regress through time. Determined to undo the tragedy, Allen relives the past, growing stronger with each cycle. In a world where sword and magic converge, where secret organizations wield hidden influence, and where demon lords scheme in the shadows, Allen must unravel the conspiracy behind Julius's possession. Bound together with a possessor and a reincarnator, three souls dance around the legendary "Feast of the Returned Demon King." Can Allen alter fate before his family loses everything?