I knew Seikio's attachment to her son had to do with isolation, but now we're left wondering why. Maybe it's gonna reveal that the husband is one of those dads who are barley home felling the wife and child to feel disconnected to him. Maybe that but also the way she gets treated by the family aswell. I initially thought she was always othered by family but it honestly makes more sense for this to start after she had Seiichi. Since her relationship with him is the main thing the rest of the family bullies her for.