7/2/15 EDIT: Fixed my previous (horrible!!) translations after more than 4 years. Thanks for supporting!!
Opening theme of Utatemeguri, sung by YuNa (遊女).
It was released in the OST of the VN itself, in... Disc 3? Not too sure.
Well, lyrics were taken from Blacksaber's weblog and yuu753's video description.
Lyrics are done, but I really have to apologise because I'm not totally sure that they are correct. I was mostly guessing... :P
http://nijinotakaramono.blog132.fc2.com/blog-entry-11.html