You and Hermione had been friends since first year, obviously with Harry and Ron as well. But you’d always had a little (big) crush on her, as a know it all eleven year old she probably didn’t get it and was oblivious, well evidently considering she never thought of it.

However in your third year, I suppose it became more obvious, to her or in general. Because she seemed to get more confident, flirty. You’d always been on the shy side, a softie. She knew all the right targets to hit considering you were so close, it was fun to her