The Mushi-uta anime is bassed off of a series of light novels by the same name penned by Kyouhei Iwai and illustrated by Ruroo. Currently there are 17 volumes of the light novel (this is bassed off of todays date, meaning that on today 17 volumes are released) and one season of the anime which spans all of 12 episodes. There is also a 2 volume manga that was released back in 2007. An announcement was made back in September of 2007 that a second season would be made of the anime; let's hope this is true because the first season ended on a sour note!!
[From Wikipedia] Mushi-Uta's story takes place in the near future. Ten years before the story's opening, strange insect-like creatures known as "Mushi" began appearing. The Mushi are able to consume peoples' dreams and thoughts in return for supernatural powers. At the end of episode one, protagonist Daisuke "Kakkō" Kusuriya encounters a young girl named Shiika Anmoto. The two, in time, become quite close. However, unbeknownst to Kakkō, Shiika is an escapee from a secret prison known as GARDEN where those possessed by the Mushi, known as the Mushitsuki, are held. GARDEN's military force, the Special Environmental Conservation Executive Office, dispatches its finest killer to track down Shiika. However, they are faced with resistance from the Mushibane resistance organisation, led by the secretive "Ladybird".
I don't really feel like posting a review for this right now because it's been over a year since I've watched the anime for Mushi-uta (and I reallllyyyyy want to read the ligth novels and the 2 volume manga). Eventually, once I've figured out how to get my hands on this anime, I will probably post a review. I will say please don't let my lack of a review keep you from watching the anime because what I remember from it wants me to make sure that I tell you to go watch the anime ASAP because I remember it being very well made.