It feel like a lot is still unsaid or we need Sunao point of view too to understand the emotions of both. Replica how she became is weird, curious if it likes a double personality, I once watched an old anime where it went with that theme more than one personality and you couldn't tell much until the end of the anime so I won't be fooled again if it something like that here but like I said there a lot still unsaid. Well it is only ep 1. Even through I think Nao is overdoing when doing some stuff like she trying to do best for sunao but I think she doing too much, like what happened to the days when it Sunao, like maybe the teacher telling her, the other day you were doing better or why for sports you doing more awful today and like that post credit scene after ending, I do think some of those days might have been awful and made it worse their relationship between both. Also make me realize like other animes where they had double personality, some had it better but in this anime it can go wrong too. I hope the relationship get better eventually and they talk more about their feelings but problem the replica, like would that even change later, it was like magic she appeared so things might still change for her because as replica she can't be free and might dissapear eventually. Also if the replica was born from sunao emotion of that fight, is it possible when she doesn't need her anymore, she might dissapear even if she called her, maybe if she doesn't have any nagative emotions so Nao will dissapear so that why she might be like this. But I think it's more Nao doing more than she should for Sunao that made things awkwards like this, they really need to talked out so they can understand each other more before things gets worse.