Jack Aaron is the strongest mercenary known by the nickname "The Bomber". After completing a heavy mission, what awaited him was a summons to another world! In this summoning, everyone is granted a special ability. However, the ability Jack was given was quite limited: "Bomb Making". The people who summoned him from the other world dismissed Jack’s ability as useless, and the other summoned individuals began to mock him as a useless foreigner.

To return to his original world, he forms a partnership with Alice, an alchemist derisively called "The Witch." During this process, Jack learns that the other summoned individuals, who he thought he had killed in an explosion, are still alive.