Action Comedy Shounen

From Tokyopop:
Gun has always been a problem kid, but after a tearful plea from his mom, he decides to turn over a new leaf. Vowing to abandon fighting and troublemaking, Gun transfers to a new high school, attempts to be a good student, and rents a room at the local coed dorm. There he falls for Seung-Ah, the dorm owner's granddaughter.
However love is not to be for this couple, as sexy Ji-Ae's untimely advances always thwart his attempts to woo the innocent Seung-Ah.