The Michigan Sex Offender Registration Act was recently amended and the new provisions may be used to help your friend get of the registry. An experienced criminal defense lawyer would have to sit down with your friend and learn much more about the case and your friend's circumstances before an opinion could be given regarding any available options.
If he was 12 at the time and charged as an adult, it must have been pretty serious. If his victim was under 13 years old, the new law requires LIFETIME registration with the ability to petition to be removed after 25 years if certain requirements are met. This applies to adult offenders as well as juveniles convicted as an adult.