Possibly some switch got flipped in Kanon-chan; one that likely says: "Hey Mikey, I Think She Likes It!" ("It" meaning *koff-koff* "bedroom gymnastics" of a rather rough nature). Then again, opinions may vary as to whether a young girl should have her first time with a partner who's so inebriated, he thinks the whole thing was just a dream.
At least Kotani appears to be a young man, who, if it came to it, would "take responsibility, right?"
Counter point. They don't know if they have anything in common other than sexual chemistry.