It is a normal day; everyone from deranged military girl Tanya Degurechaff and 16-year-old isekai protagonist Satou Kazuma to expansionist overlord Ainz Ooal Gown and demon sisters Rem and Ram go on with their daily lives. Suddenly, a conspicuous red button begging to be pressed appears before them. Overcome by curiosity, the otherworldly characters push the button, sending them to an unfamiliar world.

With no way of escaping, the characters must lead a normal school life and make acquaintances with the others. One thing is certain: the classroom full of fan-favorite eccentric personalities never gets boring!