Suddenly, dungeons have appeared all over the world in modern Japan. Omomo Rei is a genuine loner in the real world, but in the dungeon, he is the only person in the world who has reached the maximum level. Rei, who has cut off all ties with society and is completely absorbed in the dungeon, one day saves a beautiful and famous streamer, Yuria, who has 10 million subscribers, from a crisis. Rei unintentionally goes viral on Yuria's dungeon stream, and contrary to his desire for a peaceful daily life, he is drawn into the further secrets of the dungeon, which involve the underworld and even the country!