Hikari got bad grades on her midterms, but wanted reassurance from Takahashi he still liked her. I think he found a way to motivate her to do better.
Hikari held a contest to see who among her friends had the best "nibble factor." Yuki won because she was "like ice cream." Takahashi's musing out-loud that Sakie might taste the best for a vampire got him in a lot of trouble. Also, Hikari should never say in public that Takahashi's arm hair would get stuck in her teeth. She doesn't like his muscular arms, but Sakie and Kyouko do. No word on Yuki, yet.
Sakie likes to munch on potato chips while reading manga, not muscular arms. She may make an exception for Takahashi, though.