V-Rated mode:
     Successfully   complete  single  player  mode  under  the  Adults
difficulty setting.

Defeating Bosses:
     One  technique  that  is particularly helpful against most of the
Boss  stages  is to use the Slide attack. Use Slow + Slide repeatedly.
This  does  a decent amount of damage in a short time. You can hit the
Boss  four  to eight times if you are fast enough, while the Slow adds
more damage to each attack.