I would of straight up said Japanese porn and left it at that. My mom is nosy af but when it comes down to super personal you-shouldn't-nose-around-about-it business, she knows not to dig further. Porn is as personal as it gets.
"Honey, what's yaoi?"
"You remember when I forced you to watch Yuri on Ice with me? Ya, yaoi is much worse."
Yuri!!! on Ice wasn't even bad though...
Oh, sorry! I meant it as inthe sexual nature. Y'know, since Yuri on Ice is a Shounen Ai
I suspected as much. Don't mind me ╮(￣▽￣)╭
That moment when your mom asks what are yaoi and you have to sit on the couch with her and it feels like you're explaining to your child what is sex