Urahara Appears! Stop Aizen!

 is the three hundredth episode of the Bleach anime.

The battle with Aizen continues as Aizen is transformed by the Hōgyoku.

Summary
Urahara tells Aizen that its been a long time since they last met and takes note of the extraordinary form Aizen has taken. Aizen states that its nothing as midway through "evolution" is always ugly. Urahara clarifies that no one has said he is ugly, its just that he has finally fused with the Hōgyoku. Aizen explains that it isn't fusion and asks that the word "subdue" be used. He then states that the Hōgyoku Urahara failed to master has found a new master. Urahara glares down at Aizen and remarks that it's true he was unable to master it, if Aizen is referring to the past. Aizen questions his statement asking him if he's going to admit defeat. He then retracts the question making note that it shouldn't be the question. He then uses Shunpo and moves so fast that before Urahara can react Aizen impales him in the chest with his Zanpakutō. Aizen tells him that he'll forever lose the chance to drive the Hōgyoku. Urahara's body then bursts like a balloon as Urahara appears behind Aizen and places his palm against his back as he uses '''Bakudō #61. Rikujōkōrō'''. Aizen notes that he has seen the use of the portable Gigai decoy tactic in Yammy Llargo's report. He admits that he was careless as he never thought Urahara would use such a cheap trick. He then asks what Urahara will do now that he has been constricted. Urahara questions whether Aizen actually thinks that he would use just that level of Bakudō. He then follows up in quick secession with '''Bakudō #63. Sajo Sabaku and Bakudō #79. Kuyō Shibari''', which further immobilizes Aizen.

Urahara then begins an incantation with Aizen asking whether he really thinks he'll let him use that Hadō spell, but Urahara tells him its too late as he initiates '''Hadō #91. Senjū Kōten Taihō''' and Ichigo is shocked at how powerful it is. After the smoke explosion dissipates Urahara remarks at how careless Aizen has become because of his new found power. Aizen appears behind him unharmed and notes that he's correct. Urahara moves to react but Aizen slashes his right shoulder with his bare hand wounding him as he exclaims he is too late. Aizen then states that he's allowed to be careless as he doesn't have a need not to be, as he can feel the strength of the Hōgyoku in his body. He remarks that his strength exceeds that of his old self and he is now invincible, so he doesn't need to dodge a level 90 Kidō anymore. Urahara then states that he wasn't talking about dodging the Kidō, what he meant was that if it was the older version of himself, he wouldn't be letting him try his attacks on him one by one.

Aizen is suddenly trapped by spiritual energy cuffs at his wrist. He stares in shock as Urahara explains that it is a seal, which seals the reiatsu flowing out of his own palms. He then states that Aizen will now be blasted by his own reiatsu, as Aizen is enveloped in a column of light. After Aizen is enveloped in a column of light, Ichigo calls for Urahara, who tells him that the battle isn't over yet and Aizen will be coming back any second now. All of a sudden Aizen emerges from the column of light in a completely new form and Ichigo is shocked. Aizen instantly appears between Urahara, Isshin, and Ichigo and comments to Urahara about how he used a level-90 Kidō spell as a decoy to draw his attention in order to seal him with his own original technique, which would have worked had it been anyone else but him. He then corrects himself, stating that, had he not implanted the Hōgyoku in his body and subdued it, the battle would have been over. He then reaches in through the covering of his wrist and pulls out a bracelet, stating that unfortunately for Urahara, the Hōgyoku he created was beyond his comprehension. Therefore, the technique that Urahara most likely created solely for the battle with him was also incapable of reaching him. Urahara unsheathes his Zanpakutō, prompting Aizen to ask him if, since his techniques did not work, he now intends to use power against him.

Isshin comes up from behind and Aizen attempts to attack them both at once, but he is quickly blocked as they both simultaneously entangle his sword hand and one of his ankles, stretching him into an awkward position. Aizen demands to know what is going on as Yoruichi Shihōin, wearing armor on her arms and legs, attacks him from above. She smashes into his back with such force that it destroys the surrounding area. Next, she lands a direct punch with even more force, causing damage to an entire block. Urahara then yells for Yoruichi to move away. Aizen quickly recovers, and before Yoruichi can fully dodge his counterattack, he destroys the armor on Yoruichi's left leg. As Aizen emerges from the rubble with his new form severely cracked, he asks them if this all they have and says that they had better hurry up and make the next move, as he plans on crushing them all one by one into tiny fragments down to the very last remnant.

Aizen states that the number of methods that Yoruichi, Isshin, and Urahara have devised in an attempt to defeat him are equal to the amount of hope that they still have and therefore it is his duty to crush everyone of them. With that he invites the three to try their next trick as Ichigo watches on in shock. Urahara says that they are in a bind and Yoruichi's armor that Aizen destroyed were his special design that were meant to counter Hierro, stating that he never thought they would break so easily. Yoruichi demands to know if Urahara is implying that they broke because her focus was broken. Urahara denies the charge but Yoruichi confronts him and tells him that they broke because they were badly put together. Aizen points out that the fact that Yoruichi's legs are fine would imply that the armor was special indeed. Yoruichi tries to divert Aizen's compliments to her legs but then starts picking on Urahara because of a look he gave her. As Isshin watches the two of them bicker, Aizen interrupts and tells them not to bicker about what was special since the armor disappeared in one swing, meaning that if Aizen swings his sword three more times - Yoruichi's special items will disappear altogether. Urahara asks Yoruichi if she can do it, and Yoruichi says that it is simply a matter of striking Aizen with something other then her left leg but even as she says this, Aizen suddenly appears next to Yoruichi and attacks, causing a large amount of destruction to the surrounding area.

As this happens, Gin points out to Ichigo that his back is wide open. He tells Ichigo to relax, as he had been joking and invites him to watch Aizen's battle. As he says this, Urahara, Isshin, and Yoruichi are all shown struggling against Aizen. Gin goes on to tell Ichigo that his allies are going to die, but Ichigo asks him if he thinks that he will allow that to happen and then asks Gin if he knows what will happen to him now that Aizen has changed form. Gin replies that it sounds as if he has lost faith in their ability to win the battle and declares that Ichigo is just a kid after all and as such must not be allowed to die at Aizen's hands. Gin presses his Zanpakutō against his chest, causing Ichigo to wonder what the stance is for. Gin activates his Butō ability, but Ichigo dodges. Before he can react, however, Ichigo realizes that Gin's blade has already fully contracted. Gin then uses Butō Renjin, causing Ichigo to don his Hollow mask and charge towards Gin. As this is happening, Kira is shown barely conscious and he says his Gin's name a single time. He suddenly notices a still injured Rangiku running toward Gin's location. As this happens, Urahara, Yoruichi, and Isshin are shown attacking Aizen at the same time.

Shinigami Illustrated Picture Book
Shunsui Kyōraku and Jūshirō Ukitake find an old photo album with pictures from the Turn Back The Pendulum period and their days in the academy. In all this time, as they discover, The Captain Commander has retained his appearance as an elderly man. They find that they cannot recall a time when he did not look this way.

Fights

 * Isshin Kurosaki, Kisuke Urahara & Yoruichi Shihōin vs. Sōsuke Aizen
 * Kisuke Urahara vs. Yammy Llargo (flashback)
 * Ichigo Kurosaki vs. Gin Ichimaru

Powers and Techniques Used
Kidō used
 * Bakudō #61,
 * Bakudō #63,
 * Bakudō #79,
 * Hadō #91,

Hollow techniques
 * (flashback)

Shinigami techniques

Techniques used
 * Portable Gigai

Zanpakutō released Shikai: Bankai:
 * (flashback)

Other powers
 * (flashback)