There is one video performance project and three bands that go by the name Mirror.
1) Mirror are a four piece math/post-rock band from Tokyo, Japan formed in April 2003 under the name "Journal Spy Effort" as a three piece band. They release one EP in 2004 (and a self produced-demo) under this name before deciding to change their name in November 2006 to Mirror. The 10th of July 2007 saw the release of their first full-length album "On, then, in" on the CATUNE indie label.