The Greatest Demon Lord Is Reborn as a Typical Nobody, Vol. 3 (light novel): The Catastrophe of the Great Hero (The Greatest Demon Lord Is Reborn as a Typical Nobody (light novel) (3))

A BLAST TO THE PAST
Ard may think he's just gearing up for a little class trip, but the world always seems to have other plans for him. As he and his friends are riding along to their destination, a self-appointed "god" sweeps them back to ancient times-for reasons unknown. To return home, their best bet is to earn an audience with Varvatos, Ard's past self (which is definitely a little weird). Then they find out there's someone else in this version of history claiming to be the Demon Lord...! But if wading through this topsy-turvy mystery is the only way to get back to their era, so be it. Ard's never been one to back down from a challenge!