I don't super get the whole "im just the dad that abandoned him" perspective. Maybe if he really is that resentful, Satsuki wouldn't be receptive seeing his dad, but like. Mom has full custody. He can't see his kids, but if one of them is in trouble, can't he go see him?? I think it's worse in the long run that Uncle is hiding that he knows his dad. I've never been in that sort of situation before, though, so this is me just wondering.
I also wonder if Satsuki will work through his "het" attraction, or if he'll discover gay people exist and he's one of them.
The dad just left, and from what I can tell hasn't had contact with Satsuki ever since. It also appeared that the dad was the only role model that Satsuki had. I think it's reasonable that the dad make an attempt to see things from Satsuki's perspective and recognizes the potential consequences of overstepping on Satsuki's feelings, even if the assumptions he has is ultimately wrong. It's just the safer move for the father to proxy the relationship rather than risk the alternative.
And maybe you might be thinking it's not a big deal to just try and make contact directly just once. Maybe I'm projecting from my personal experiences but when it comes to this level of resentment even the act of trying to make contact is seen as a hostile action. The mother rejects Satsuki's mere presence, and thus it's unfortunately reasonable to acknowledge that it is possible for Satsuki himself to pick up this dysfunctional thinking pattern from the mother, despite his best intentions.
You may want to argue that, because it's a proxy relationship, it's become a betrayal of trust regardless of how Satsuki feels. But there are different levels of betrayal. The risk/reward calculation is that it's better to commit a guaranteed low, but sustained perceived betrayal, rather than coinflip everything on one giant gamble upfront. Again, since even making contact can be perceived as a slight, maintaining any sort of information travel at all is super important in setting up the foundation to rebuild a relationship
