Isshin Shiba & Masaki Kurosaki vs. White

 is a battle taking place during The Rise & Fall of Masaki Kurosaki, centering on the conflict between 10th Division Captain Isshin Shiba and experimental Hollow White, which Quincy Masaki Kurosaki intervenes in partway through.

Prelude
Upon learning of a series of unusual Shinigami deaths in Naruki City, 10th Division Captain Isshin Shiba heads to the Human World to investigate and has the two Shinigami patrolling the city stand by so he can lure out the killer. Some time later, near the south gate of Naruki City, Isshin stands on a rooftop, with the two Shinigami observing him from below and musing that the rain is coming down hard.

When one of them questions what they should do and brings up Isshin telling them to leave, the other reminds him that it would be crazy to go back to Soul Society since they would just be punished for it and asserts that they should stay here for now since they will be safe with Isshin present. Simultaneously, Isshin internally theorizes that the enemy is either targeting Shinigami or just reacting to high Reiatsu, leading him to decide to lure them out by exerting his own powerful Reiatsu.

Upon seeing this on the ground below, the two Shinigami are awed by Isshin's Reiatsu, but one of them has his head cut horizontally in half from behind. Alarmed by the cries of pain from below, Isshin stops exerting his Reiatsu, realizes that the size of the Reiatsu is not what the enemy is attracted to, and sees two bloodstains on the ground just before White crashes into the rooftop behind him. When the dust clears, Isshin is astonished to see a black Hollow standing before him while White looks back at him.

Battle
With White growling prior to roaring loudly, Isshin examines him and mentally notes that while White's body is black and the hole in the center of his chest is filled with a mass, his Reiatsu is unmistakably that of a Hollow, causing Isshin to ready himself for battle while White rushes toward him to attack. Following this, Isshin flips back through the air, where he internally chastises himself for already being on the defensive, and clashes with White, whom he notes fights like a Shinigami despite his appearance. Mentally admitting that this is making it difficult to fight, Isshin is pushed back through the air by White before a Shinigami approaches to inform him that Karakura Town is under the Thirteenth Division's protection.

Upon realizing that he has been pushed out of his jurisdiction, Isshin warns the Shinigami to run, only for White to rush toward and obliterate him with a Cero fired from between his horns. Isshin expresses disbelief at White being able to fire a Cero like a Menos prior to clashing with White once more, where he muses that White could not possibly rampage like this without Soul Society noticing him and questions who is covering up the incidents for him, though White remains silent. Unsurprised by White not answering, Isshin moves back and releases his Shikai, Engetsu, coating his sword in blazing flames. However, before Isshin can attack White, he is slashed across the back by a cloaked 5th Division Captain Sōsuke Aizen, who had noticed the fight from Soul Society.

Isshin falls to a rooftop below, where he realizes that he was cut by a Zanpakutō rather than a Hollow and that there is a traitor planning this within the Gotei 13, prompting him to demand that his attacker show himself. Above Isshin, Aizen explains to 3rd Division Captain Gin Ichimaru that he did this in order to prevent Isshin from stabilizing his Reiatsu enough to activate his Bankai, as White is a failure if he cannot defeat a captain using only their Shikai, and apologizes to 9th Division Captain Kaname Tōsen for referring to White as a "prototype" instead of by his name due to him being created from Shinigami Souls. Down on the rooftop, Isshin blocks a heavy downward slash from White, causing blood to spurt from the wound on his back, and stomps on White's free arm to prevent him from attacking with it while internally noting he cannot focus his Reiatsu enough to use Bankai.

Despite this, White manages to fling Isshin into the air with brute strength and leaps after him, prompting Isshin to warn White not to underestimate him, draw blood from his back wound into his mouth with his free hand, and spit the blood wound onto Engetsu, creating a horizontal pillar of flame that detonates in a large explosion upon making contact with White. Having sensed the conflict from the Ishida estate and decided to intervene despite the warnings of Ryūken Ishida so she would not live a life of regrets from letting an innocent die, Masaki Kurosaki reaches the site of the battle below.

Seconds later, Masaki sees White's severed left arm hurtle out of the smoke and embed itself in the ground near her. Above her, Isshin is impressed to find White continuing to clash with him using only his remaining arm. Suddenly, White pins down Isshin with another downward slash and begins charging another Cero between his horns that he aims directly at a startled Isshin. Before White can unleash the Cero, he narrowly evades a Heilig Pfeil fired by Masaki, who stands on the pavement below with a Heilig Bogen formed, prompting Tōsen to promise to eliminate her since a Quincy getting involved was not part of the plan.

However, an excited Aizen stops him and expresses interest in seeing what happens before White rushes down, with Isshin's ankle injury preventing him from following. Masaki fires dozens of Heilig Pfeil at White, and with the latter evading all of them with ease, she decides to change tactics and disperses her Heilig Bogen, leaving Isshin urging her to run and Aizen startled. With Masaki holding her left hand out to him, White reaches her and bites deep into her left shoulder, only for Masaki to calmly note that she has got him, form a handgun-sized Heilig Bogen in her right hand, and fire a powerful Heilig Pfeil at point-blank range through White's head.

Aftermath
With Isshin, Aizen, Gin, and Tōsen watching in shock, White's shattered corpse begins falling away from Masaki, only for the mass in his chest to suddenly swell up behind him, prompting Isshin to rush down and pull the corpse away from Masaki just before it detonates in a massive, one-sided explosion, which Tōsen is alarmed by. In the aftermath, Masaki runs over to a prone Isshin and frantically asks him if he is okay, which he confirms. When Isshin thanks her for saving him and mocks himself for needing to be helped by a young girl despite being a captain, Masaki counters that he would not have been so badly injured if he had not protected her from the explosion, which prompts a laughing Isshin to observe that they are even now as Masaki promises to heal him. However, with Isshin wondering who she is since she was able to defeat White, Masaki internally debates what she should do since she does not know how a Shinigami will react to learning she is a Quincy.

Despite this, Masaki introduces herself as a Quincy to Isshin, and though initially stunned by this, a smiling Isshin admits that he has never seen a Quincy in person before and claims that he feels lucky to meet one like this. Surprised by Isshin's reaction, Masaki wonders if this is what all Shinigami are like and laughs as well while expressing hope that this is the case for the sake of Izumi, Ryūken, and the other Quincy. In the air above Isshin and Masaki, Ryūken stands with Katagiri while holding solid Spirit Weapons with her and asserts that they can leave since Masaki is safe without any problems, which Katagiri acknowledges.