In a world where the battle between Hero and Demon Lord repeated itself time and time again, an enormous space-time spell misfired and hit a certain Japanese high school class on Earth, killing everyone in it. However, guided by what seemed to be a miracle, the students were all reincarnated into that other world. While a handful was fortunate enough to become royalty, nobles, and other kinds of influential people, one girl was not so lucky.
Being reborn as a spider monster of the weakest kind in a dungeon filled with vicious beasts, she is forced to experience extreme hardship. Even so, armed with nothing but her human knowledge and overwhelming positivity, she continues to press on and survive against creatures much stronger than herself.