A long, long time ago, a female priest, Kiyoko, held 8 different stones. Each stone had a heart carved in it. The stones were red, orange, yellow, green, blue, purple, pink, and gray. The stones held souls of 8 girls in them.
They held very powerful power, that sealed the devil deep within the core of the Earth. (That's why there is iron in the core of the Earth).
Kiyoko protected these stones from demons, and evil humans who wanted to use the power for sin. So she cared for the stones, cleaned the stones, and some days, she even said the stones gave messages to her. In return for the stones company, she protected them.
One day, after a fight with a strong demon that wanted the stones to himself, the demon sent out a giant evil vibration across the land.
Days and days later, the gray stone began grow black. The girl's soul in the gray stone became wicked more and more, day by day. Kiyoko knew that once it turned fully black, and the soul was completely malicious, a giant destruction would come upon the worlds, along with the one she cared most for, Earth.
She knew what she had to do; she had to destroy it. She destroyed the stone, but the girl's soul still lived. The girl did not. Her soul wandered but still became more evil by sunlight hours. Kiyoko disappeared 2 years later.
Years and years later, the stones were intercepted into 8 different young girls. One with pink hair, one with blue hair, one with red hair, one with green hair, one with yellow hair, one with orange hair, and one with purple hair, one with gray hair.
All 7 (not the gray stone) of them lived in one town, known to no one other than the people inside it, called Volya. No one can come out, and no one can get in. The gray stone was keeping that promise.
Of course, the gray stone wants destruction, and she started to do bad things, until the day she disappeared. She arrived in town, but only to cause violence. Sooner or later, someone had to do something!
The 7 girls loved to sing and dance so they auditioned for a new band, and they all won. The manager told them about fighting and transforming to defeated and delete the evil in Volya.
The weird thing about their fighting is they transform and use music. Their manager's name is not yet to be spoken of, they just call her Ana, short for manager. But, she says her name is Yokiko. She has started a girl band with all 8 girls. Right now, they are in training.