In all seriousness though, Nagi's father personality change was pretty extreme to a point where if this wasn't as cute as it already is I would have dropped the shit out of it. Good thing I'm able to just enjoy the fluff with stuff like this.
About the father personality change, I guess you could say that he treats Nagi differently in the end because she’s already an adult, not a child like before. Still, a bit sudden tho.
"hows the dads personality change so much" presumably its been like 20+ years, and also shes an adult now instead of a 5 year old. it's not that surprising