Though on a serious note, most of these films have men who cheat on their girlfriends/wives....so I looked it up and a couple of US newspapers had articles on how the men in Moscow have this culture of having a side-thing going...don't know how much of it to take seriously.. but it is a trope that keeps coming up in these dramas.
My cousin who lives in Japan says there too it is expected that the husband might have a mistress outside. That women are quite accommodating and feel like their husbands need such outlets considering how hard they work outside....
Asianboss did a docu-video on this. I don't know what to make of this.