Show By Rock!!

Synopsis

Thanks to the efforts of Darudayu and Shu-zo, Cyan manages to use her music to purify the Dark Monster, freeing Rosia and the other Criticrista members. Just then, Dagger makes his appearance, using his power to take everyone captive in order to sway Cyan into joining him. Before Dagger can contaminate Cyan's Melodisian Stone, he is stopped by Grateful King, who managed to escape thanks to the efforts of Maple and his assistant Angelica. As Dagger prepares to use his full power against Cyan, Grateful King blocks Dagger's attack and sends Cyan back towards her own world. Not wanting her friends to fight Dagger alone, Cyan unleashes her own potential and uses her power to defeat Dagger, returning him to his original form. With the battle over, Plasmagica give one final performance before Cyan returns to her own world, where she works up the courage to join her school's music club.

(Source: Wikipedia)