Just started this elsewhere. I saw someone say that you could basically cut out most of the early chapters and it would be a better story, and I find myself agreeing with that. The whole 'warming dad up to build a relationship' is implied to be the overall premise but the story itself is frankly awful during the short arc that actually deals with that. I'm enjoying it a lot more now that I've started the part where they are warmed up and still building the relationship but also doing other things.
The thing I think also needs to be emphasized is that the reason that early arc is terrible has to do with how illogical and frustrating some of the details are. I get the impression the author wanted to base it on actual absentee father relationships but it just comes off nonsensical how they did it. I might be biased against 'defrosting family members' type stories but I know I've seen better variations somewhere.