Dynasty forums be like...
Some thoughts:
I'm really enjoying the diverse representation. Sure, it feels like it gets a bit textbook-y at times, but you have to keep in mind that these are topics that many people have trouble understanding, or might not have even heard of. It's particularly uncommon to hear about how "asexuality" is an umbrella term and that it's actually a pretty wide-ranging subject that encompasses much more than just disinterest or repulsion towards sex. Speaking from the perspective of an ace-spectrum person, I'm fine with a bit of over-explaining if it makes it easier to follow the story for someone who otherwise wouldn't really know what was happening. People on dynasty are usually more knowledgeable about queer topics, but the average reader doesn't know as much, if they even know anything at all.
The fact that Matoi goes from definitely seeing herself as aroace to considering whether she might be some other kind of asexual is nice. She's still young, and her understanding of who she is and what she wants is probably still in some state of flux. She might end up deciding that she was right the first time, or she might not, she might even decide she's not ace at all (though I highly doubt that's the case, for a variety of reasons). My best bet at this stage is that she's gray ace (which I'll admit is in part because just about everything but that has been covered by a different character :P) I'm really glad she has people around to help her discover who she truly is. Rio especially. She seems like she really cares about Matoi, and will respect Matoi's feelings and boundaries (that is, now that she has learned what Matoi's feelings and boundaries are. Remember, kids: just because your japanese mangas have people confessing by suddenly kissing someone, doesn't mean it's okay to do in real life! :P)
While I'm sure some people would like it if Yuriko eventually returned Matoi's feelings romantically, I'm personally hoping they enter into more of a queer-platonic relationship (especially after that incredibly cute bit of snuggling at Matoi's apartment. My heart...) They're both calm, relatively mature people (for manga characters), I think they're definitely capable of finding a way to be together that makes both of them happy. I expect the ending to be something along those lines, but we'll see.