平凡会社員の成り上がり迷宮録

One day, towers all over the world turned into dungeons. The Tokyo Tower was no exception, becoming a labyrinth (Meikyuu). Those who were unfortunately there during the transformation were all swept up and went missing. Shirou Konomi, an office worker, was also one of those who lost his family to the tower's transformation. To him, a strange high school girl named Akari comes to visit. She is also someone whose family was swallowed by the labyrinth, and she asks him to dive into the dungeon together to search for them... Thus, Shirou made the decision to challenge the labyrinth alongside Akari.