According to the official blog, the theme song of "Bakemonogatari
" is produced by a music artists group supercell. The title is "Kimi no Shiranai Monogatari" and the single CD will be released on August 12th. Gazelle, a popular singer in Niconico Douga, sings the song instead of Hatsune Miku
supercell was initially an amateur creator group, which uploaded VOCALOID Hatsune Miku songs to Niconico Douga.
"Koi wa Sensou" by supercell (Youtube)
"World is mine" by supercell (Youtube)
They made a debut as a professional group on May 4th by releasing an album CD from Sony Music label. Mangaka Miwa Shirow
is one of the eleven members.
Source: supercell official blog
ryo, the leader of supercell, also writes the theme song of "CENCOROLL
". It will be bundled with the single CD mentioned above.