Something mysterious happens and an entire class finds themselves reincarnated in a RPG-game-like fantasy world. The main character, a girl, finds herself reincarnated in a spider. Will she able to survive and to find out what happened?

The world where the Hero and the Demon King continue to oppose each other. The grand magic from the Hero and the Demon King cross over worlds and exploded in the classroom of a certain high school. The students who died in the explosion will be reincarnated in a different world. Kumoko who has the lowest reputation in the class, was reincarnated into the form of a spider. Nevertheless, she adapted quickly to the present condition with strong willpower. This is a story of she who has become, a spider trying whatever she can to live.