High school student Boji Nichiro is isolated from the rest of the world due to fierce bullying. One day, however, the world is transformed by the "dungeonisation" phenomenon! In the midst of the chaos, Nichiro awakens the unique skill "Shop". It was an out-of-the-box skill that allowed him to buy everything from food and daily necessities to unrealistic items!

In an RPG-like fantasy world consumed by warring nations and racial discrimination, the human kingdom summons five high school students from 21st-century Japan for assistance in their conflict with the demonkin. Now those students, with their experience of MMORPGs at their disposal, will hone their skills to protect the human kingdom of Edea. However, this isn't their story. Out of the five students, four of them were given the title of Hero and the fifth one the title of Innocent Bystander. He had been summoned by accident since he sat near the other four students. His name is Hiiro Okamura, an aloof bookworm with traveling and reading as his raison d'etre. Hiiro sees no reason to help the human kingdom in their offensive war with the demonkin, seeing that he isn't a Hero and that he has no real obligation to help them, and decides to leave the kingdom to go on his own adventure. Soon, Hiiro finds out that he has the very unique skill of Word Magic: magic that can materialize the definition of a word. As he travels more and more, he finds many uses for his Word Magic and many opportunities to find books, level up, and gain some of his own companions. Even with the outbreak of war on the horizon, Hiiro stays true to his desire to travel the new world he's in.