Yukiya is the self-sacrificial type. I think I saw this coming. He left the whole "friend group" because he didn't want to make Miku uncomfortable. But really, all that did was drive a wedge between them and make her uncomfortable. He didn't bother to ask Miku if she liked hanging out with him more than with the girls.
I think this arc is gonna help Yukiya blow past his insecurities. Mihashi's gonna help him be more outgoing like before, and Fuji's gonna help him be more confident with his chances with Miku. At least, I hope it's gonna be like that.
Miku still seems to be badmouthing Yukiya a bit too much here. She's not really making Yukiya unattractive to the other girls. She's just making him look bad.