I recognize this artwork.
Its the same mangaka as the one that did
"Kin no Kanojo, Gin no Kanojo"
which is a great series of triangle Ecchi romance with a lucky pervert MC.
So they're taking on the Isekai trope with a bang of a first chapter, it's very interesting premise indeed and suit the author so well.
if it goes along like last, the guy will be a pervert, as usual, but loyal to the girl he likes, so harem is unlikely, that's probably a good news for you people that doesn't like that tag.