C1-3: About a college student/private tutor and the high school student he's teaching who has a thing for him.
C4-5: About childhood friends. One of them is super popular but when it's only the two of them, the popular one is actually very mean.
C6-7: A teacher and a student. The teacher is a really strict guy and the student is trying to do things to show sensei that he likes him but the teacher just wouldn't believe him.
C12-13: Host after a night of drinking drunkenly sleeps at a neighbor's place instead of his own. From then on, after eating the breakfast the neighbor made, he has been coming over for food but for some reason his neighbor seems familiar.
C15: Haruka, Kaede's younger cousin with a big gap of personality, is going after this stoic classmate of Kaede who's actually a gentle soul but for some reason always gets thought of as cold.
Katekyo!