OK, I'm calling it. This is going to be a supporting harem series. Emphasis on the "supporting". I initially thought that Miori didn't include him in her list of "hot guys she's interested in", but her frustration and disappointment with his treatment, combined with the occasional flirtatious lines, tells me he's definitely in the list. Maybe not a full crush, but his looks combined with their past at least make her think it'd be a nice path and feel a little annoyed that he doesn't seem to see it. Again, "supporting": she knows he has someone he likes and so lets it go with some minor annoyance or disappointment that someone she seems to have thought liked her in the past has moved on, choosing instead to wish for her happiness.
Given that Yui is best friends with Hikari, I'm sure this will end up the same way: she recognizes him as a catch, maybe even likes him a bit or feels her heart flutter around him, but she's not going to pursue a guy who's already in love with someone else, nor is she going to try and take her best friend's crush, at least not without a lot more pushing her forward.