Mimori Touka and his classmates are summoned to a fantasy world by its resident goddess to serve as heroes, but Mimori's abilities prove to be a major exception. He's an E-rank, the lowest rank possible, and his skills seem useless in the new world. However, when the goddess banishes him to a dungeon, it becomes clear that his abilities are actually extremely powerful, despite being abnormal. Mimori sees this as an opportunity to survive and eventually exact revenge on those who discarded him.