Is there a manga or novel where in a protagonist is isekai'd on an already isekai manga or novel they have read? Like Original novel -> first Isekai (the protagonist have read) -> Second Isekai (which we are reading)?
Considering how your typical isekai reads like, I don't even want to imagine that... P.S. Guess the closest we have to that is something like the CN Quick Transmigration (QT) genre.
That's uhh I only know https://www.novelupdates.com/series/little-tyrant-doesnt-want-to-meet-with-a-bad-end/ But he gets sent to the past instead.
An anime called Isekai Quartet Welp I read your request incorrectly. The easiest you can find are SI/OC fanfics of isekai stories. Good luck though.
Can you guys help me find this one on Japanese so i can read it. Ore ga Inmajutsu de Dorei Harem wo Tsukuru Hanashi 俺が淫魔術で奴隷ハーレムを作る話
The closest scenario I could think of are novels/mangas where the returnee protagonists are either recalled to the same other world that first summon them or forcing themselves back
Transmigrated into a Noble's beaten son (tapas.io) Trash of the Count’s Family - Novel Updates My Death Flags Show No Sign of Ending - Novel Updates not novel but a game.