Luca was used as a non-regular porter for the D-rank adventurer party "Flap of Fire". He believed in the leader Zash's words that he would accept joining if he had the guts to do chores without pay for two years and worked hard, but Zash forgot the fateful day when joining was decided, and Luca was expelled from the party. But the party without Luca didn't go as well as usual... Born in the demon world and raised in a family of heroes, the strongest adventurer's exhilarating fantasy adventure begins!