Dunno man, I just feel like Kotone-senpai's a weak contender. Her start was strong, sure, but the author could only provide fanservices when it comes to her chapters. Compare it to Suzu or Chiaki, or even Nonoka really, since we've seen the chemistry between Daisuke and them. While with Kotone, it's probably along the line of "getting hypnotized to see her naked" or something.