Most Japanese games have VA's that do a great job.I don't know what kind of game you mainly play nor which Sexual Sounds you mean, moans? or the meat slapping sounds.
For me I mostly play Japanese games and the moans + voice acting can be found mostly in VN, I sometimes find in RPG style games too but only with the ones with a big company.
For the "meat slapping sound", "ejaculation sound", wet sound effects etc. I've never seen JP game without these ones yet.
Even if he did, it would still be terrible if it's not then implemented correctly. Excepted Asian games, almost every time the sound make us hear a girl near to orgasm while the MC is still just kissing her ; what is totally stupid.Unless a dev is willing to pay a few thousand for a professional VA to do the sounds then it's not worth the time.
Btw any devs reading this thread, make sure you include options to turn off/adjust volume of sexual sounds.Because most of them sound terrible and aren't worth the time.
I can't fault the voice actresses themselves but most Japanese games do not sound "great" to me. Granted neither do Western ones but there I can at least distinguish "porn moans", "no! help!" and "girl enjoying it" most of the time, and while cringy most of them aren't physically uncomfortable while the high-pitched squeals are.Most Japanese games have VA's that do a great job.