Arashi was orphaned as a child. Both of her parents had died. But, the head of the Ise shrine came and got her and took her to live at Ise.
There, she became the hidden priestess of the Ise Shrine. She is the shrine's most powerful preistess and has obtained all of the shrine's powers. She will be the shrines final gaurdian.
Arashi also has a sword the comes out of her hand that she can summon at any time. And it is the realy object of worship at Ise, the sword is extremly sharp and she handles it very well.
Arashi is one of the Seven Seals, or Dragons of Heaven. When she meets Kamui, she knows that he is the true Kamui, but he has not yet truly awakened. Hinito, the dreamseer who lives in the basement of the Diet Building, told Arashi to protect Kamui. And so Arashi does.
Arashi can be very cold and completly un-emotional. But later in the series, she starts to mellow out and actually some times becomes a softy.
Arashi is one of my favorite characters, she is very mysterious and cool.