How do I get my gf to want to have a threesome with her sister?
watch anime
>>17319640
You dont.
You shame her into it
Make her feel terrible and blame her for making you feel like shit and not helping you achieve your goals in life
Abuse here mentally for as long as needed, with increasing cruelty
She'll break eventually, and when she does she'll enjoy it because you'll tell her it was all okay and felt good.
>>17319640
the hardest part is convincing the sister, I'm guessing. get close to her first.
>>17319829
Pretty much this.
Although I'd add drugs into the mix. Great for tearing into someone's self-esteem and capacity for guilt and also distorting their values.