Ah! I always end up in NTR game while trying to find a FMC corruption game.
I think NTR is more believable/reasonable in Magic/Supernatural/Paranormal settings.
In the Erona Hentai Manga, the FMC agrees to sex with the Orcs she was sent to destroy because the Orc leader traps her teammates, including her BF, with deadly magic and curses her with a lust mark. The curse makes her enjoy his advances, erases her past with each climax, and ultimately turns her into a loyal NTR heroine. And the team was captured not because she wasn't a good fighter but because of her BF and team members looked down on the orcs even though they heard rumors that these orc group is different and can use magic. Later, the BF uses his soul power to break the magic, rescues FMC who regains her old memory, and they nearly kill the Orc leader.
A year later, the now-married couple struggles with sex cause BF used soul power and can't perform well!! And year earlier when they returned FMC suffered severe trauma because of her actions under the curse. To help her Healers lock away her memories of the Orc leader, but her body still craves the pleasure she experienced. So she goes on a lust-fueled rampage (gangbang etc under disguise), and Eventually, she remembers everything and resolves to kill the Orc leader for what he did to her. But when she finds him, he shows her a vision of his death, which triggers another breakdown as she realizes she can't be satisfied by mortals and desires the Orcs' barbaric ways. And finally joins him.
And why the Orc leader wanted her all along because he needed a woman with high stamina and mana to birth dark elves his ancestor. Sorry for my english and long summary.
I recently played a game A Trouble in the Arena, if you can stomach futa on female (+ honey select 2) & futa NTRing MC's harem then you'll absolute enjoy it. It has humor & great scenes.