Megumi Hitokiri is a lonely 19-year-old boy, heir to a clan of assassins. He hated his family, who robbed him of all they were precious to him. He wanted to leave this world, then suddenly someone appeared before him. Presenting herself as Lukia, a god, she proposed to him to reincarnate and defeat the demon king. He was a bit wary, but eventually accepted, and began his new life with a skill called Prodigy/Tensai.
Several years after his reincarnation, he formed a group with which they had many adventures and then finally, after long battles, they managed to defeat the Demon King. Having done so, one of them was to become the new administrator, but they were all brutally murdered by one of the members of that same group, who then became a god. At the same time, Megumi wandered into the abyss, and he vowed revenge. He reincarnated again, this time in a completely different world. But this time, her goal was clear: to become a god, defeat the traitor, and kill anyone who stood in her way.
