I think that if your hair is naturally black, adding more bright blue or red streaks would be a good idea if you wanted to do J-rock, and styles that seem to be popular are ones that are choppy, but not messy, and that don't go much past your earlobes. I have tried to insert an image that might be helpful, but also remember that J-rock hair styles can often be tricky, and high maintenance.
Best wishes,
mangafreak
