Rather than cheating, maybe they were both single moms already that got close when their husbands went away (deceased) - hence there was that question mark kind of feeling when the other said "regards huh".
Maybe they also dislike it in their own way. So the mangakas come up with these fluffy fanarts hoping the official will be the same. If I had the skills and time I'll be glad to give these two a happy ending right now. Sigh......
Eventually Kou actually did went to overseas. As of now, I only remember one chapter or two that have her in it. Christina's sister is like an alternate version of Hazuki
Awww dayum. 2nd part seems like it will be fun though lol.
Ahhh so this is where Matsuri said she's Harumin's girlfriend. I remember Nene saying something like "oh it's the girl who said she's Harumin's gf" or something like that in one of the more recent chapters and was wondering when that occured.