Princess of Tenshi Heisouban Shihouin. She is also known as the Goddess of Flash because of her mastery on using Shyunpu (flash steps). She became the leader of the Executive Militia, which is the first branch of the Covert-Op Division. This divison is ranked the highest in the 5 branches. Covert-Op is in charge of punishing and assassinating ex-comrades who break the law and they also act as scouts when fighting Hollows. The wonderous things our great Second Division Captain had to do, eh?
Whether she was Captain of 2nd division I'm not sure, I'd like to believe she was so she is. :p
She remained unmatched in melee combat and led the Miltia while being the Tenshi Heisouban Shihouin family's 22nd Chief of the house and is the only woman to ever hold that position.
Yourichi scouted, who is now Second Division's Captain Soi Fong, as one of her bodyguards because Yourichi felt she had potential. Later on she was to be hunted down by her own division which she had led, for assisting the exile Kisuke Urahara, 12th Division's Captain, escape Soul Soceity. Because of the warrant issued for her arrest she laid low for 100 hundred years and took the form of a black cat to elude her captors.
Though she was out of commision for said hundred years doesn't mean she got entirely weak. She could still kick butt as she proved to us in Chapter 157 - 159 and again later on in the series.
Let's re-cap shall we?
