Otherworld summoning Gates ( Multiverse isekai)

( I won't cover how big the world is though but through each chapter you could potentially fill it in the world itself is at least partially original and fantasy based could potentially have sci-fi elements if you guys wanted to. The core elements of this theme is people get summoned whether males or females [or futas if you want] and get stuck in situations where they either meet monsters people or items that ultimately result in sex)

In the world of Lumeria a number of gates ( not specified number) these are the Otherworld summon Gates originally created by the Gods to prevent the world's destruction by summoning beings from outside to help save the world due to them not being able to use their powers to their full extent in the Mortal plane. After many years too long to tell could have been centuries or thousands of years or even million who could say but eventually the purpose of the gates was forgotten except myths about them but most people didn't even believe those except for the gates which had either cities built around them or near them most of the locations where they were have been lost to time one for instance was swallowed by the sea, another, sank to the the sand, one had a cave system form around it they're also more (you guys can make your own locations). Now the world of Lumeria has a number of different races that call at home there's most obviously the human race then there are the Beast races The Monster races and the demon races magical races and then finally the demi-humans which aren't really a race more a category for those who don't really fit into the others but generally have a humanish appearance but none of them would ever have thought that after all this time that the summoning Gates was suddenly start working again.

( just a few examples of some of the races so you guys can add more if you want. demons incubi succubi, monsters Goblin and Orcs, beasts Kitsune werewolves, magical fairies Elementals, demi-humans dwarves and elves. Note that among the races there can be a number of varieties even in a single race)( another thing you can either take it from the summoned persons point of view or the point of view of a person from this world)( one final thing about the races if you think that some races aren't in the proper category you can swap out to the one you think they should be in or you can simply if you feel the need to create a new racial category)