See movies at Japan Loves U Blog
A song called "Love" of girls heavy metal band "Death Devil" in Manga K-ON is now in the ranking of itunes.
"Death Devil" is not a real band, it is a band in the manga, however a real CD was released on 23rd June, 2010.
K-ON is a manga describing the story of high school girls rock band.
As far as there is manga fun, a product, music, food... anything in the manga will be produced as "real" product from various manga.
Imagination and virtual world of manga will be a little bit real things with those real goods in the story.