Soushitsu Mahoutsukai no Saikyou Kenja - Uragirareta Moto Yuusha wa, Ore Dake Tsukaeru Saikyou Mahou de Anyaku suru

[The hero who was betrayed by the entire nation in his previous life unleashes his unparalleled, one-of-a-kind, strongest magic!]Hero Lecter, burdened with the hopes of his people, trains diligently every day to defeat the Demon King. As the time for his departure approaches, a man calling himself a "transmigrator," Baylif, suddenly appears. He challengesLecter to a duel, saying "whoever wins will be the hero," but is defeated by Baylif's overwhelming strength, which is impossible in this world... Months later, Lecter wakes up to find that Baylif has already defeated the Demon King and is being worshipped as the "hero"—!? Sensing something is wrong with Baylif's evil aura, Lecter attempts to fight back, but is scorned as a "former hero," betrayed by his people, branded a demon, and loses his life.It seemed as though he had ended his life in despair, but he obtains the now-unavailable strongest magic, "Loss Magic," and is reincarnated into the world 10 years later. In the world 10 years later, magic has declined at the hands of Baylif. Only Lecter can save this world—the former hero becomes the strongest sage and saves the world from the shadows!