Game set in fictional recreations of Japanese red light districts feature porn stars... checks out to me.
But on another note, Yakuza loves to cross promote in Japan, this goes from restaurant promos, getting various celebrities and real people to appear in the games as themselves (including celebrity chefs, a Judo fighter, and a weird dude who showed up to an audition in just his underwear)
This also extends out to AV stars, originally it was mainly/only for the hostess dating side of things, but along the way they started using them for other stuff - 0 features quite a few porn stars, you'll notice (or maybe not, if you dislike the cards) that a bunch of the ones your collecting are for women that appear in the game - the hostesses yes but also the lady that helps Kiryu's real estate business (Marina I think?) is a real porn star.
And then you have Yakuza 6 which just basically drops all pretense of using the characters in other mini games and just lets you chat to actual porn stars as they undress.
Though I'd need to check to see if 7 actually has porn stars in it. Usually (as mentioned above), its for hostesses but the hostess clubs are just stat boosts in that game and feel like an afterthought, not sure they bothered to get real girls this time? The only ladies I remember being added to the game were competition winners from a talent search and those were the basically the girls (bar Saeko) that help you in side content - Eri was the winner and such she's a party member and part of the big side content (and as a bonus, amazingly overpowered and the best party member in the game, go Eri!) but also the modding shop lady, the woman that works at the class switching job center, the bar tender at your hideout and the lady at the quiz mini game reception area.
