Ninero Nakamuzo, a 16-year-old young man, is walking in a park when something strange happens. While walking through the park, he finds a cave he’s never seen before. He ends up entering it and, when leaving accidentally, he trips on a stone and falls into a huge hole inside the cave that sends him to another world. A world where a creature named Enir Reality Eater is devouring the entire world, slowly destroying it. Ninero will have to survive in this world and figure out what that hole was and how to get back home.