Hirotatsu Kurase, a high school boy living a mundane life, stumbles upon a mysterious QR code on a utility pole while taking a detour on his way home. Out of curiosity, he scans it with his smartphone, triggering the download of a mysterious game app called "Dungeon Seekers." This app, using the phone’s camera function, allows him to enter a dungeon filled with rampaging monsters—a bizarre and extraordinary phenomenon begins…!?