so in short, this is about an ace girl's story of falling in love? It'd be nice if the mangaka would continue making Yuu analyze every situation rather than just go along with it without questioning things. This is interesting.

I don't think she is asexual but rather aromantic because in the last chapter of the 3rd volume Yuu says that she does enjoy being kissed just like anyone would. So I think that means that she does feel sexual attraction or at least enjoys it but doesn't feel romantic attraction. Perhaps she is gray-romantic or demi-romantic. I guess we will see.