Here is Greenwood (Koko wa Greenwood) Manga

Kazuya Hasukawa is lovesick: the woman he loves just married his older brother, and now she's coming to live with them! Unable to face the harsh reality, Kazuya decides to leave home. The only route of escape is to enter the exclusive all-boys boarding school, Ryokuto Academy, but since a car accident sidelined him for quite some time, he missed over a month of school. At Ryokuto Academy, Kazuya is introduced to the Student Body President, Shinobu Tezuka, and Kazuya dorm's Head Resident, Mitsuru Ikeda. The two come across as nice, handsome young men. Kuzuya will later learn that they are quite the pranksters. They escort Kazuya to his new home - a dorm called Ryokurin-ryu - but because the name is a mouthful, everyone calls it by it's English name, Greenwood. Arriving so late in school, Kazuya is assigned to the last available room in the dorm, and paired up with his least expected choice for a roommate - Shun Kisaragi, the cutest girl in the guy's dorm! Shun's parents have raised her as a boy and Ikeda and Tezuka implore him to keep her secret between the four of them. [Viz] Review @ AnimeOnDVD

This is such a well loved, classic shoujo comedy that I'm glad Viz is handling the adaptation. The Here is Greenwood anime was just released on DVD for the first time in 2004, after being a fan favourite for years on VHS.

Here is Greenwood/Koko wa Greenwood Anime

The entire 6 episode OAV on one DVD.