Shiryoujutsushi Weltz no Heiwa-ron

In their quest to achieve world peace, the Hero's Party has succeeded in defeating the Demon Lord at the journey's end. But victory came at a heavy cost - the Hero, the Saint and the mighty Warrior all perished, with only the Sage, Weltz, as a sole survivor of a hard-fought battle. Thanks to their sacrifice the world peace has been achieved... or so it should have.