I think if they talk about mixers and alcohol, it's a safe bet it's college. For some reasons, the college experience through the eyes of hentai is "I need a girlfriend" and "look at me, I can handle alcohol."
I don't see how alcohol at a mixer really means much, TBH. At least, it doesn't mean much for Americans. You can judge the state of things here however you want based on this, but it's actually pretty common for 15-year-olds and even younger to get their hands on booze and weed and get wasted at some party. Stronger drugs, like acid, meth, and speed, are much less common in general, but still show up here and there. (Some places have those much more often than others, ofc., especially huffing / Tide pods / meth.) Something like coke is pretty rare from what I've seen, other than at parties at some rich kid's house or w/e.
I'm also not sure why you brought up hentai. While there are several, ofc, loads of adult games are
not hentai or even similar to hentai. So themes presented in those lewder anime / manga don't typically have much influence over AVNs in a more Western style. There are, of course, Western-made games that will specifically play into the Japanese tropes, but that varies quite a bit, and I've seen a lot more than don't than that do.