Hana no O-en Step

Hiromi is a girl who often gets mistaken for a boy, and she winds up connected romantically with a young man with some girlish mannerisms after he gets assigned to the girl's dorm at their high school due to over-crowding issues.

(Source: Animeraider)

Included one-shots:
Volume 1: Senaka ni Hana wo Shotte, Kibun wa Mou Seihoukei
Volume 7: Zenmaijikake no Shinzou no Oto
Volume 8: Kin no Lame Furu Escort, Manhattan Syndrome