Warning: The following contains spoilers for BLEACH: Thousand-Year Blood War Part 2 – The Separation, Episode 3, "The Fundamental Virulence" available to stream on Hulu and Disney+.

In the third episode of BLEACH: Thousand-Year Blood War Part 2 – The Separation, titled "The Fundamental Virulence", the Quincies have launched another surprise attack on the Shinigami, this time bringing the division between the Seireitei and the Wandenreich to a collapse for the sake of war. After the Quincies plundered various Captains of their Bankai, the newly disempowered Captains all come up with various ways to make up for their lost combat potential, to varying results.

Lucky for them; however, Kisuke Urahara has devised a new creation that will not only return the stolen Bankai to their rightful owners, but also make the Shinigami immune to future Bankai theft. Here is an explanation to the Urahara invention, the Shin'eiyaku.

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Breakthrough

Urahara Kisuke contacts 12th Squad Captain Mayuri Kurotsuchi about his findings regarding the Bankai that were plundered, and even knows how to create immunity from future incidents through a means we've seen in BLEACH before: Hollowfication. Urahara's logic in coming to the conclusion that instilling Shinigami with Hollow reiatsu to reach the aforementioned result was that in the incidents leading up to the first invasion, the Quincies had taken special military interest in Hollows, specifically the Arrancar, taking them prisoner and putting them on the front lines. The Arrancar are the key to Urahara's understanding of the mechanics informing both the Quincies and their medallions because they are beings that have transcended normal Hollows, gaining Shinigami-like powers after breaking their masks.

The Arrancar have a technique analogous to the Bankai called Resurreción, in which they unsheathe their "Zanpakutō" and activate it much like a Bankai. Despite this major similarity, no Resurreción has been stolen, and it can't have been because Quincies had no interest in them. Urahara arrives at the scene and speaks to Kurotsuchi directly, asking for his cooperation, bringing him up to speed about what he saw in Hueco Mundo during Ichigo's fight against Sternritter J – The Jail, Quilge Opie. Urahara could only think of two reasons why:

1. Resurreción cannot be plundered, or;
2. It would be disadvantageous to do so.

Kurotsuchi quickly understands what they're dealing with: a fundamental incompatibility with Hollow reiatsu, which resonates with something that has been bothering him about the Quincies for quite some time.

The Fundamental Virulence

The word "virulence" refers to the damage caused by a pathogen upon its host, while "pathogenicity" refers to an organism's ability to cause disease within its host. Kurotsuchi tells Urahara that he's always found something strange about the Quincies' hostility towards Hollows. He believes that hostility and resentment are borne from differences in ideology, which would perfectly describe the Quincies' relationship with the Shinigami; however, according to Kurotsuchi, it isn't possible to maintain hostility towards those without will or ideology.

For Kurotsuchi, the only thing that reconciles this inextinguishable hatred with the Hollows' general lack of will is the idea that the hatred stems from fear – the fundamental fear of that which threatens one's life. Urahara adds that Quincies do not have a path to Hollowfication like other souls do, highlighting the urgency of their need to exterminate them because if they are killed by Hollows, their souls are simply destroyed. To that end, Hollows are much more accurate polar opposite to the Quincies. As such, the episode title, "The Fundamental Virulence" brings to the fore Urahara's discovery of the reason for the Quincies' fast subjugation of the Hollows prior to their invasion of Soul Society, as well as their seemingly wasteful decision not to plunder Resurreción.

Shin'eiyaku

Urahara's observations of Ichigo's fight against Quilge Opie helped confirm the poisonous nature of Hollow reiatsu to Quincies. In that battle, Quilge absorbed the Hollow beast Ayon into his body, dramatically changing the appearance of his Quincy Vollständig; however, there was evidence that he could not fully control the power as his form crumbled while being overwhelmed by Ichigo. This fight was crucial in Urahara's creation of the Shin'eiyaku ("Shadow Infiltration Pills"), black pills that are absorbed into the soul upon contact. Within these pills is a small amount of Hollow reiatsu that permeates the depths of the soul, meaning that they also affect the Zanpakutо̄, and thus, affect the Bankai whether it has been stolen or not.

The pills help Hitsugaya and Soi-Fon briefly escape situations that were certainly going to lead to their deaths, and they inflict major blows on their opponents. Once the pills have been administered, the Quincy medallions are affected, and those who used Bankai in combat were soon afflicted by them, enabling even the badly injured Hitsugaya and Soi-Fon to unleash and land critical hits. Daiguren Hyо̄rinmaru's appearance was "Hollowfied" in his response to Cang Du, and he was able to overwhelm his opponent with what appeared to be a somewhat augmented version of the Bankai. With the "cowling" aspect of Hitsugaya's Daiguren Hyо̄rinmaru, the extent of Hollowfication seemed quite significant with Hitsugaya in particular as his voice also gained the unholy quality that the Visored get when they don their masks.

BLEACH: Thousand-Year Blood War Part 2 – The Separation, Episode 3, "The Fundamental Virulence" is available for streaming on Hulu and Disney+.

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