Now also Yuki Goto has been added to The Possible!More: http://www.berry-cute.com/?relat=374So it's 5nin now!! But the article mentions that Yuki might not yet be included in the CD release for The Possible. The release date for now is 22th October, and the rumoured song title is "Young Days".
And according to this http://ikimasshoi.jphip.net/index.php/?p=654 they are no longer part of UFA