Yoruichi is shown as a very strong willed and intelligent woman. She always carries an air of knowledge about her, as if she always knows more than she is letting on. She is a very dedicated character once she focuses on a particular task, but otherwise she settles back into her usual routine: in her normal life, Yoruichi is more of a laid back slacker, almost a slob. She eats a lot, dresses perhaps a little too casually and often slings herself over chairs sideways and eats at snack foods or drink. Despite this, she secretly keeps up her training when she can, and remains one of the most powerful characters, able to best a Captain when she was self admittedly 'very out of practice and slow'.
She also possesses very strange mannerisms and ways of speaking: she often speaks in very old fashioned dialects. This can be attributed to two different causes: first, she is of noble lineage... in fact she is actually a princess to the noble clan. Her mannerisms are likely attributable to her being a rebel: having been restrained so much when growing up, and possessing a free spirit that endured, she tries to let herself go as often as she can. Secondly, she is actually very old: as a spirit being she is ageless, and will continue to live forever (short of damage or other cause of death) so her mannerisms and way of speaking were picked up in another age.
She also has spent a long time as a cat, so her sense of self and societal norms are actually very rusty: when she first re-became human in appearance she was naked, which freaked the teenage Ichigo out, it took her a moment to realize what was wrong. She also terms herself 'washi' which is a male term in Japan for old men, which shows just how long she has spent as a cat (when she becomes a cat, she becomes a male cat, it is unknown if this is by choice, but it is likely considering her rebellious nature and the fact she did not want to be found as a cat). Of course another aspect of her personality was revealed when she first became human once more: her bizarre sense of humor. She has since then become naked in front of Ichigo from cat form just to see his reaction, which she finds hilarious as he freaks out. She often teases him in this way.
She is shown to have a fondness for Kisuke Urahara, whom she grew up with and often stays at his place. It has not been revealed if this fondness is just friendship, or something more.
Yoruichi is the ex-captain of the second division: a division that is formed as a special forces and assassination division: her followers were skilled rogues, assassins and ninja's. Known for their stealth and subtlety: Yoruichi is no slacked in these departments herself. She is born of a soul society noble clan named the Shihouin family, which is one of only four noble families in Soul Society. She is considered a princess by her people. She has a long history with Kisuke Urahara who used to serve under her, and also Soifon, whom used to be her closest friend. Though her age has not been revealed, in recent flashbacks she is shown as an adult even over a hundred years ago, and has a strange relationship with Byakuya Kuchiki, whom she calls 'Little Byakuya' and teases often. She is shown as a full grown adult when he was only a child.
She grew up in soul society with Kisuke Urahara and the two trained together, eventually becoming very powerful due to their dedication. Kisuke early on revealed his intelligence when he created a magical training place where they spent much of their time together. When she became one of the Soul Reapers, he became a seated officer below her. Later on, he also became a Captain at her recommendation and apparently easily completed the tests to prove himself of captain power. At this time she also developed a strong bond with one of her guards named Soifon, who would eventually take her place as Captain when she left soul society for the real world.Yoruichi helped free Urahara and Tessai after they were arrested. She caught wind that something was wrong in Soul Society after the hollowfication of several high ranking Shinigami what would become the vizard. Urahara,Tessai,and Yoruichi would leave with the fallen shinigami to hide in the real world until finding out what was really going on.
Soul Society Arc
Yoruichi makes her appearance after Rukia is taken to Soul Society for execution and Ichigo wants to save her. Yoruichi takes responsibility of training Chad and Orihime to develop their unique powers. Once Urahara and Yoruichi feel everyone is ready the journey to Soul Society begins.Urahara opts to stay behind while Yoruichi leads the humans to reach Rukongai, a spiritual district for human souls not of nobility. She reveals Ichigo and others need to find a way into Seireitei where the high class nobles and shinigami abide. Ichigo rushes to defeat the guard Jidanbou. She urges all to withdraw in approach of Captain Gin. Everyone is allowed to escape as Gin decides not to pursue. Yoruichi brings Ichigo and others to meet an old friend named Kukaku. It turns out that Kukaku knows a method to break into Seireitei using her Kukaku Cannon. Everyone is split up in entering Seireitei as Yoruichi gets by roaming around in her cat form.She finds Ichigo in time to save him from his injuries dealt by Captain Kenpachi. Ichigo is the first of the humans to see Yoruichi in her true form. Yoruichi later saves Ichigo again when facing Captain Byakuya once again while Ganju and Hanataro attempted to free Rukia. She knocks the pretensious teen out as he was set to fight and uses flash step to elude Byakuya,much to his annoyance. Yoruichi decides to teach Ichigo means to achieve bankai in a matter of days while it takes years for normal shinigami. Once Ichigo is ready Yoruichi gives him her Tentoken Cape that allows Shinigami to fly through the air. While Ichigo arrives to save Rukia four captains are present after subordinates are easily taken out. Shunsui reveals to be interested in facing Yamamoto to end the tradition of killing those who break trivial laws. Only Soifona and Byakuya remain and Yoruichi comes to remove Soifon from the equation. The two begin to duel in a forest backdrop using hand to hand combat. Soifon reveals her rage of abandonment by her mentor, and best friend for hundreds of years. She dedicated all her days to becoming stronger than Yoruichi so that she can kill her. Yoruichi is forced to use her Flash Cry,a technique Soifon was only starting to use. Yoruichi and Soifon stop after Aizen's betrayal is announced to all. The pair unite to stop Aizen from releasing his sword. Aizen decides to withdraw with Gin and Tosen his follows. The traitors leave for Hueco Mundo the world of the hollows.
Yoruichi comes to save Ichigo from death in facing Yammy,the 10th Espada and Ulquiorra. She hurts herself from performing hand to hand combat on a being with flesh that was hard as steel. Yoruichi tries to keep Orihime below Urahara's Shop after learning Aizen may be after her. Unfortunately Orihime is told it was due to her being weak and she is bothered.
Powers and Abilities
Yoruichi is a very diverse character, and she possesses many powers and abilities that set her apart from others.
In her first appearance, we see her as a male cat. She can apparently shift to this form at will, and it is not limited by time. She had apparently been a cat for a very long time before her appearance, as when she first shifted to human form she was ungainly, unbalanced and unused to being human, commenting that it 'had been a very long time since she had been on two legs'. She seems to be limited in that she can only switch between cat and human form.
She is a master martial artist, able to take on opponents armed with Zanpaktou (shinigami spirit slaying swords) with only her fists and feet. She was even able to pulverize an Arrancar whom had iron skin with only her martial arts, while being completely un-hittable by the opponent, though afterward she was shown with her fists wrapped in bandages commenting that it had hurt because she was still out of shape.
Yoruichi holds the prestige title of 'Goddess of Flash', a praise that refers to her complete mastery of the Shinigami short range instant teleport known as 'flash step', which is a combination of super speed and teleporting. She is legendary for it: and even when over a hundred years out of practice she was still able to outmaneuver Byakuya, who had been training himself for all that time to take the title off her, yet she still commented that her comparatively 'sloppy' flash step was more than he could handle.
As a shinigami spirit being, Yoruichi is ageless: immortal in lifespan alone. She also possesses Kido magic (Demon magic) to a high level, though she seldom uses it: preferring to be a physical combatant when she fights. She is also able to walk on air at will and also has a few special techniques that she developed herself, including the 'flash cry' which sheath's her body in energy which she can use for blasts and personal deference.
She possesses two highly powerful and magical items, both of which lend the wielder the power of true flight.
The first is an arm strap and wand that at will can protrude a bat-like wing which enables the user to fly. The second seems to be a cloak and brooch that is superior to the former item in that it also allows the user to hover in place and use both arms, this item however seems to display the crest of her family: likely a heirloom.
Nothing is known about Yoruichi's zanpaktou, she seems to disdain its use after soul society, seemingly preferring to fight hand to hand and use her special techniques.