I think I read this manga way back - it's a oneshot wherein the girl is a delinquent/puts on fancy make up and the guy is a strict president disciplinarian comitee. Then later on this girl found out the the vice president of the disciplinarian comitee is the ex of the guy. Later on after this girl confessed to the president she changes her style - into a normal HS girl - no make up whatsoever. but then it's the disciplinarian comitee who changed his style into a more angsty look.

Possibly the extra story, Fake, at the end of Underground Kids.

Good luck!

or could it be the second story in 100% gokuama kareshi!?

it' 100% Goakuma Kareshi! thanks Marshy!