1. Gender Bender... The main character should be a guy, and a pathetic nobody at that, who gets them selves gender bent into a girl, and a super hot or cute chick magnet at that, who can easily make any girl question their orientation... and the gb event should happen because the mc actually asked for it, or at the very least, they should find the change a welcome one...
2. Isekai... The main character should find them selves in a pre-industrial fantasy world of magic, swords, etc... OR... In a super advanced, "clean", scifi world... but either way, a "feudal" society, with abusive and entitled, kings, queens, princes and princesses, nobility, etc... no democraziness, no pollution, no fire arms... probably... But definitely Monsters of some sort, regardless of whether its fantasy or scifi...
3. Aphrodisiac soaked Hentai / Fetish world... Regardless of whether its fantasy or scifi, there should be latex and other fetish outfits, bdsm, sex toys, etc, etc, etc... And the abusiveness of the nobility and royalty should be of the sexy sort... ie. they're into "bdsm" that is borderline safe and sane, but by no means consensual, and keep abducted commoners in their private sex dungeons... And all monsters should be of the rapey, aphrodisiac spewing, mind breaking hentai types...
4. The main character could be OP, with some pervy abilities of her own, and go on some world conquering quest, building slave harems of horny girls, but ultimately end up in some hentai type "bad end"... like brainwashed into some ecstatic sex slave of some orc king or something... or they might be, weaker and get enslaved almost immediately, or many times, and keep going from one nasty master to another, but ultimately endup a slave of some hot princess or duchess or such, with sexy, kind but strict oneesama personality, who offers to let her free... but the mc falls in love with her... or its a match made in stockholm... or the mc was always a pervert who enjoy what is happening... or its sometime more insidious... but either way the the mc chooses to reject the offer for freedom, and they live happily ever after...