
I know what you mean...but I also think I can sympathize with wanting to show off to your friends when you're proud of something. Like it seemed like he was proud of how good looking his boyfriend was and that somebody so cute/cool likes him. Even if it seems vain who wouldn't in all honesty feel that way in the same situation... I don't think the point of that extra was to make it seem like he liked Satoi less when he dressed like a guy, but that he wanted to be able to show off how good looking he was and that they were together to his friends. They obviously aren't going to speak about their relationship being gay to his friends and I doubt his friends would be able to appreciate how good looking his boyfriend is as a man so then he isn't excited about sharing that with them because it isn't in a context they would understand.

I like how you're comparing apples and oranges. One is Soutarou being scared that he's not good enough for Satoi when seeing him Mifune. And Satoi not being angry because of how superficial it is, SERIOUSLY Soutarou brought up how Mifune is kind and understanding and has never bullied him, sorry he had more than simply 'Mifune and Satoi look good together' for his insecurities. Satoi was more angry at his doubt of Satoi's love, NOT of how superficial it is.
Second is Soutarou simply wanting others to feel envious of him for having such a pretty girlfriend. Why would Satoi feel bad about that? Satoi himself is happy when Soutarou compliments how his girl form looks. Is Satoi now superficial? You literally took two things that had nothing to do with each other and compared them.

First of all, when Satoi dresses as a girl it's something he always loved to do and was always invalidated for. It's part of who he is but was never accepted for until Soutarou came along. But even if that's part of who he is, Satoi also likes being a man equally whereas that seems to be something Soutarou does not appreciate or consider as much in their relationship. Hence why it feels so superficial from Soutarou when he feels insecure about how Mifune and Satoi look better together and wants to capitalize on Satoi's pretty appearance as a girl
So the first couple ends just like that? I honestly think those extras made their relationship worse.. I found it extremely distasteful when Inugami was expecting him to dress as up as a girl just to show him off to his friends. Like did you learn nothing? After all Satoi hated the fact that Inugami felt superficially he was better looking with Mifune and that Mifune would accept it ┑( ̄Д  ̄)┍