It's not that hard to make these kinda games, all it needs is a LOT of time to learn and practice. Credits to the ones who actually end up making good VNs. Its funny also how there is no "danger" aspect of not letting the husband know like you suggested. Either their husbands are just simple dumb fucks or they are purposely kept in the shadows and she keeps on teasing like a fucking boring movie. Most of these VNs follow the same format:
Release - MC gets fucked by partner, erotic scene at the bedroom when she wakes up (to get the tags), there's always an old man as neighbor for some reason.
Update 1, 2, 3, 4, 5, 6, 7, 8 - MC teassssesss.............................