High Teen Boogie

Momoko is one of the brightest students at school, but the school is a bit overrun by delinquents from a motorcycle gang. In fact, the person who has the next desk has never come to class. Then one day she gets the upper hand on one of these bikers and they actually strike up a bit of a friendship, with the potential for more. Of course, it turns out that he's the leader of the bike gang, and the student in the next seat who has been missing this entire year...

(Source: Animeraider)