A brief description of the Nidome no Yuusha manga:
Ukei Kaito is a hero called to the new world. He has already managed to fight with the Demon Lord and defeat him. Despite his feat and saving humanity from misery, the hero was betrayed by the most dear people. And now, the hero’s chest pierced the sword of “friend”, and his last words was a promise to prevent such a trust next time. Now his goal is revenge on those who took advantage of his trust. He has no right to be weak and merciful. But will it be “next time”?