Hanayo and Rin are characters who's major traits aren't just what define them, but how the traits are used, which makes them overlooked. I planned on making a small post about Hanayo for her upcoming birthday though. Just a bit on what I mean, to use the shyness, Umi is shy for the sake of being the "strong girl with the weak side", a typical (and loved by many) combination of traits. Ordinarily, shyness is just an "adds on to the rest of the stuff" type of endearment. Hanayo on the other hand is based on this trait alone, and there's where her purpose comes. Instead of it just being a trait, it defines her purpose. She dreams of being an idol, she wished she were more out going, but her shyness is the factor that stops her previously. The same goes for Rin and wanting to express her feminine side more but couldn't.
I feel like tbis post was low quality and my thoughts are being ordered poorly, so I apologize, I'm running on 3 hours of sleep, starting my day at 10:30am, and the later I go to sleep, the more tired I am later -_-