And here it is. So he and Rie fought because he didn't love her anymore. Worse if he was already cheating on her before the divorce, which seems to be implied here. Bastard. At the very least Riri should light up a smoke right in front of him. I'm happy Rie finally got named, but this guy can stay nameless so I can keep calling him cheating bastard whenever I want.
Well, not only was he not there for her for years, I suppose he didn't pay any child support either, since he already had a second family to deal with. He's lucky his daughter is a softie sweetheart and didn't grow up to hate him.
Kou is typically a male given name, so I guess this means Riri has a half-brother somewhere.