Dare ga Yuusha wo Koroshita ka

A prophet announces that a hero destined to defeat the Demon King will emerge from a village. The villagers place their faith in this prophecy due to a boy proficient in both swordsmanship and magic. Eight years later, the boy fulfills the prophecy by becoming the hero who defeats the Demon King, but he vanishes afterward. Four years following his disappearance, as records of his deeds are being compiled, the mystery surrounding his death begins to unravel.