#1 The main character finds himself in a fantasy world full of elves, dwarves, orcs, and magic. He sets out to create a harem for himself, just like any isekai protagonist should. Unbeknownst to him, the demon maid he summoned has other plans. She wants the MC for herself. In order to accomplish this she will seduce and conquer any women that tries to get between them. Or adjacent to them. Or who just so happens to be in the vicinity. She's not picky.
#2 Eeking out a meager living beneath the soul-crushing weight of a corporate world. Technically alive, but hardly living. And what’s worse, born with a penis of below average size. What’s a man to do? Die and get reincarnated into a fantasy world? Well, it’s funny you should mention that… Our hero, henceforth known as Donkey, is reborn into much better circumstances. Money, education, magic, he even has a beautiful elven fiancée! Yet, reincarnation was unable to cure Donkey of middling penisism. Now, everyone knows that an isekai protagonist is supposed to get a harem, but how could one possibly enjoy it when one’s schlong is slightly smaller than normal? Oh, the humanity.