Kyou, Koi wo Hajimemasu

Tsubaki is a girl who loves making her younger sister's hair pretty every morning, but she doesn't think that kind of style suits herself! On the day of her High School Opening Ceremony, after she failed to be the top student (who usually makes the ceremony speech), she finds herself sitting next to the actual top student of the 1st years, the worst rude guy ever, Kyouta. Because of his saying bad things to her she purposely cuts his hair. Kyota requests that Tsubaki pay him back "with her body" but Tsubaki pays him back by fixing his hair and making it even shorter! Afterwards, Kyota unexpectedly kisses Tsubaki and swears he'll make her his woman.

(Source: Shoujo Manga Maniac)