I know the dad isn't innocent. His neglect contributed a lot to Seiichi's suffering and the unhealthy environment they lived in. But I hate seeing him blame himself for everything. While yes, his behavior certainly didn't help, Seiko is responsible for her own actions. A lot of the things she endured and blamed on others was her own fault. Like when she blamed Sei for being born. Like ma'am you chose to have him. She chose to marry the dad, and she to react the way she did. Things turned out the way they did because she was meticulous and evil in her ways of abusing him. So it's sad to see him blame himself for everything because not everything is his fault.