Hamelin no Violin Hiki

Synopsis (en anglais)

While on their quest to stop the Demon King, the violinist Hamel, the pianist Raiel, the magess Flute and the female warrior Sizer stop in a small kingdom and destroy a rampaging monster. While giving the four a heroes' welcome, the king and queen explain that their daughter has been kidnapped by a monster living in a nearby castle. They agree to go and rescue the hostage princess and defeat the monster. However, the enemy's castle is heavily guarded... (Source: Anime News Network)