Kyou Kara Ma no Tsuku Jiyuugyou! - Vol. 1 Ch. 2 - I'm What?!

[MangaDex]

 

[Mystyc_Cheez]

So this manga is 20 years old, yet already seems not uncommon for the idea of a hero to be defeating a demon king to be a thing. Just how old is the genre of isekai!??!?!?!

 

[Spoonikle]

Transportation to ikemen world via ladies room toilet flush...