According to NHK website, Itsuki Natsumi’s manga “Hanasakeru Seishounen” will be animated. It will be aired from April 2009.
“Hanasakeru Seishounen” is a Shoujo manga published in LaLa magazine from 1987 to 1994.
Source: NHK
Edited on Dec 2nd==========
According to Itsuki Natsumi’s blog, it’s a 9-month series and the production company is Studio Pierrot.
Source: Itsuki Natsumi’s blog
Edited on Dec 6th===========
Mainichi News has a key illustration of the anime.
Mainichi News
According to NewType magazine, the staff are as follows:
Director: Kon Chiaki (“Higurashi no Naku Koro ni”)
Series organizer: Ikeda Mamiko (“Kyouran Kazoku Nikki”)
Character designer: Kusumoto Yuuko (“Victorian Romance Emma”)
Production company: Studio Pierrot
Source: MOONPHASE