Really? I think Kouko manages to be creepier to Miyako.
Why though?
Unlike Miyako, Kouko was content with simply follow Miyako around, only starting to get more hands-on after she actually got on speaking terms with Miyako. Plus, she always comes off as relatively level headed most of the time. ; Miyako on comparison has always been on creep mode form the get-go and is a mess of a person in every aspect of her life. To not mention that Kouko is not a lolicon like Miyako.