its not really a villainess but the mc trapped inside that kind of world and the character that his in was supposed to kill the prince/duke
should i write you love letter instead
another similar one is I think my friend will become the devil where he’s a minor antagonist (think cale from the lout of the count’s family) but with a huge twist
https://www.mangago.me/read-manga/i_think_my_friend_will_become_the_devil/
stuck in my sister’s dating sim is probably the best example of the villain isekai bl genre but no where near the level of peak some villainess out there are https://www.mangago.me/read-manga/stuck_in_my_sister_s_dating_sim/
I do have a super tiny list with villain bls (some aren’t bls) I also haven’t read them all so read through the warnings https://www.mangago.me/home/mangalist/3447552/?filter=&page=1
Is there a villainess type of manhwa but just switch the gender the mc is male