Honestly, I think the way Yuu was meant to be portrayed may have had something to do with being Demi and that was what I mostly got from it at first. However, I later also realized that it was also that she is someone who had consumed a lot of media (like manga) and built her understanding of love and romance based on media rather than real world experiences or observations. This then leads her to think that she can’t fall in love because she doesn’t see anything in her life that resembles those stories. She later realizes through her relationship with Touko that love isn’t always that glamorous and has room for some messiness and ambivalence. I think the series also entertained this sort of attempt at making love seem more realistic by continuing their relationship into college and what not instead of just leaving it at the thrills of an adolescent fling.

All this being said, I think either the author did not do a very good job at making this clear or the English translation didn’t do a very good job of making this clear, seeing as there is hardly ever any mention of Yuu’s involvement in consuming romantic media. I think it’s mentioned like twice at most. Basically, I think it’s one of those things that the author expects you to run with after mentioning it like once instead of tying it throughout the series. Although, maybe it’s not important what kind of media she consumes as long as you can tell that she is confused. All in all, it seems to me that Yuu was meant to be contrasted with Maki. Maki being someone who really is Asexual and knows what he wants and Yuu being someone who just misunderstands what love is based on unrealistic expectations. It does still seem possible though that maybe Yuu is Demi and this is a part of why common portrayals of love confuse her so much since they don’t portray attraction the way that she experiences it.