"I don't really want kids" + "We only have sex when I start to get backed up"?
It's almost like he's asking for it. Hell, I wouldn't even be surprised if it turns out he invited his friend over specifically for that to happen.
And it's obviously because he's trying to get her more desperate for it, I know that, but I can't help but feel like he's being weirdly...Kind? By not progressing things any further and giving her (and by extension her husband and his Senpai) another chance over and over without escalating things too much...But her husband is just kind of an ass, that or he just doesn't care, or he actually knows and wanted this to happen.
At least he...kind of...improved a little by the end? If that ending leads to them having a happier married life and the other guy backs out, would that make him...a wingman for their marriage?