The hit shonen series Bleach stars a sprawling cast of characters, and hero Ichigo Kurosaki is just the start. Ichigo makes many friends and allies during the major story arcs, especially the Soul Society arc, and never would have succeeded without the rogue Yoruichi Shihoin's help. Yoruichi was a vital ally against Ichigo's nemesis, Captain Byakuya Kuchiki.
Yoruichi and Byakuya in fact have a history together, defined by rivalry and competition. Decades ago, Yoruichi teased Byakuya with her superior flash step and agility, and a hot-headed Byakuya declared he would one day defeat her and prove himself the best. If these two Soul Reapers fought for real now, who would win, and how?
What Yoruichi Shihoin Can Do
Yoruichi Shihoin was once the Captain of Squad 2, and for good reason. She was trained to be the ultimate master of stealth and assassination, and no one beats her at her own game. During her Captain days, Yoruichi was no doubt sent on many missions to spy on or assassinate all manner of criminals and rogues across the Soul Society, and she was the one who trained the future Squad 2 Captain Soi Fon. Yoruichi only lost her rank because of Sosuke Aizen's villainous schemes, being forced to rescue Kisuke Urahara from twisted justice and then going rogue.
Like all Soul Reapers, Yoruichi possesses a zanpakuto -- but she rarely draws it. Instead, she takes many foes by surprise with her famed martial arts and combat skills. Yoruichi's speed, dexterity, agility and strength are all incredibly advanced, and she can even take on a tough Arrancar like Yammy Llargo and drive him into the ground without much effort. All this is backed up by Yoruichi's extensive training as a stealthy assassin, allowing her to easily find and exploit any weakness in her opponent's strategy or abilities. Her unparalleled use of the flash step technique earned her the nickname "goddess of flash." In fact, the flash step is the basis of Yoruichi's and Byakuya's somewhat one-sided rivalry.
If that wasn't enough, Yoruichi invented her own fighting style, a hybrid between traditional kido spells and martial arts called shunko. Yoruichi envelops herself in an electric shunko aura, boosting her physical combat skills even further. She usually gets her hands on any equipment item or weapon she needs, from a magical glider to a long bandage that can stifle a zanpakuto's shikai release.
What Captain Byakuya Kuchiki Can Do
As the future head of the noble Kuchiki household, Byakuya received the best training and tutoring any boy could ask for in the Soul Society, particularly under under his grandfather Ginrei. One day Byakuya met the rambunctious Captain Shihoin and beheld her incredible flash step in person. A rivalry was born, and even the adult Byakuya, despite his hot-headed ways being behind him, remains determined to outperform Yoruichi.
As a Soul Reaper Captain, Byakuya has a remarkably diverse and flexible fighting style, even if he is not the most powerful Captain of them all. His swordsmanship is top-notch, and his unarmed combat skills are impressive for a non-specialist. And, of course, he can perform the flash step to a highly advanced degree, outpacing nearly everyone except Yoruichi and the 7th Espada, Zommari Rureaux. The first time he and Ichigo fought, Byakuya moved too quickly for the hero to even see, let alone react to.
Byakuya's shikai can overwhelm enemies with a thousand sharp, petal-like blades, and his bankai, Senbonzakura Kageyoshi, is the same thing on a grander scale. He also makes heavy use of defensive and offensive kido spells alike, ranking among the most elite kido users of all. He doesn't typically use forbidden spells or any spell ranked #90 or above, though.
If Byakuya & Yoruichi Had Their Rematch
The duel between Yoruichi and Byakuya is bound to be short, since neither will get a chance to use the full extent of their powers such as Senbonzakura Kageyoshi or shunko. Instead, this battle is being fought almost entirely through flash steps as each Soul Reaper tries to outpace the other and gain a favorable position. Byakuya is good at this, but Yoruichi is better still -- this is her specialty, after all.
If Yoruichi is serious enough, she could keep one step ahead of Byakuya the entire time, especially with her elite assassin training backing her up. Her instincts and reflexes are better (and more bloodthirsty) than Byakuya's, and before too long, Yoruichi can finally corner her opponent and deliver a single barehanded strike to knock him out bloodlessly. And just in case, she can use that bandage to seal Byakuya's zanpakuto and ensure it never releases its true power. If the duel is based entirely on flash steps and physical combat, Yoruichi is certain to win -- even if Byakuya attempts a kido spell.