
I don't know why are you blaming the uke. In his past life he thought seme destroyed his family and forced him to be with him. So, of course he would ignore everything concerning the seme. He probably didn't even know how horrible his health was. He just didn't want to have anything to do with him.
After he died he found out that there was some misunderstanding regarding his parents. And that seme was actually caring about him. So of course he wants to treat him better now.
MC is a little bit too dumb and trusting for someone who's been through few miserable lives. Even tho she looks sweet and cute, she is not really eight years old.