It doesn't feel like a denial of emotion but rather her emptiness
haha at no time in no shape of form have I felt emptiness from Yuu, pretty much the opposite I think she's too nice at times. Just because she wasn't blown away by some heart beat event for Nanami yet doesn't mean she doesn't have feelings and is indifferent, and err well I am expecting some super nervous interactions to come from how the stories going (really I can't wait!)
I used to think like Yuu too so with being able to relate and with how much love is sensationalized when young I feel that the main characters have had great character growth in the short series and the dynamics (interactions) between characters are both believable and very interesting!
I hope you get to see Yuu's cute side :P (also I don't know a human yet who's not a little crazy lol)