It is an ordinary day; everyone, from the unhinged military girl Tanya Degurechaff and the 16-year-old isekai protagonist Satou Kazuma to the expansionist overlord Ainz Ooal Gown and the demon sisters Rem and Ram, continues with their daily routines. Suddenly, a conspicuous red button that seems to beg to be pressed appears before them. Overcome by curiosity, these otherworldly characters push the button, sending them to an unfamiliar world. With no way to escape, the characters must lead a normal school life and make acquaintances with one another. One thing is certain: the classroom full of fan-favorite eccentric personalities never gets boring!