Haikara San is a high school teacher struggling with the harsh reality of the homeroom class he’s been assigned to—a far cry from the teaching life he once envisioned. One day, when he tries to stop a group of students from bullying a classmate, a mysterious voice echoes throughout the classroom and the entire building is transported to a dungeon in another world! After awakening his skill to befriend monsters, Haikara sets out to conquer the dungeons.