Uncle doesn't seems like the person to take action, so prob Kana and him together isn't really going to happened. Uncle got his chance and let it go. Kanna can't really pick up a relationship by herself, Uncle is just...too with the flow of things, which isn't a positive.
Now, Aya is coming to terms with her feelings little by little, the one who isn't really up there is Mitsuki, she got a lot going on and I don't think is focus on exploring things with Aya yet.
Let's remember that Mitsuki is a shy girl and the only outlet of expression and freedom she got is music, so is hard for her to fully understand her own feelings sometimes more so being an adolescent < worst shit possible to sort out your own feelings if you don't get someone who can mentor you to try and understand life and yourself a little better, cause by god I know Uncle try to mentor Mitsuki but damn he can't cook for shit.