The first thing that caught my eye about her (physically) was the longer lock of hair on her left, which she keeps her ribbon tied to it. It looked a bit strange at first yet very original compared to other hairstyles in animes.
Gotta admit it ... she looks great just the way she is, Rin is one lucky son-of-a-gun who doesn't quite deserve a great girl like Asa but that's the way things go hehe.