From Viz:
The more Wedding Peach and her friends Yuri and Hinakiku discover about their new-found magical powers, the more Rain DeVilla and her evil henchmen vow to destroy them. In the never-ending battle between love and hate, three young girls are the world's last line of defense against the onslaught of evil.

Main story is in vols.1-6. Vol.7 is a recap volume.

From Tokyopop:
An ancient seal has been broken, sending a flood of demons into the mortal realm. Hizuru Oborozuki and Takuya Hijou, descendants of the great savior who banished the demons in the past, must fight the evil spirits using their mystical powers. In order to give the world a fighting chance, Takuya uses his music to transform Hizuru into a beautiful warrior. Some things are worth fighting for, but is the Earth one of them?