Recruit from the Nest of Maggots

 is an event where Captain Kisuke Urahara recruits Mayuri Kurotsuchi as part of his plans to establish the Shinigami Research and Development Institute and make the 12th Division his own. During this, other events involving Kaien Shiba, Byakuya Kuchiki, and Gin Ichimaru occur.

Prelude
The day after Kisuke Urahara is formally inaugurated as the new captain of the Twelfth Division, Hiyori Sarugaki arrives at his office and is shocked by the changes he has made and makes her displeasure known. She demands to know if he thinks he can just change whatever he likes in the captains office.

Urahara is forced to patiently remind her that the office no longer belongs to her former captain and is his to decorate how he pleases. He asks her to learn to understand this and he will learn to understand her more and more. In response, Hiyori aggressively punches him in the face, causing a nosebleed, but Urahara responds by asking her to accompany him to the Nest of Maggots.

In the Second Division's headquarters, a member of the Onmitsukidō reports that Urahara wishes to enter their grounds, claiming to have already received permission from their captain. Yoruichi Shihōin struggles to recall giving him such permission so the messenger asks if he should ask Urahara to leave since she cannot confirm whether she permitted him entry.

Unconcerned about the issue, Yoruichi decides to allow Urahara access to their grounds unhindered. The messenger is surprised and wonders if she has now recalled when she gave him permission to enter the area. Yoruichi denies that she has recalled the incident, but does not rescind her previous order. Suì-Fēng protests against these orders, but Yoruichi tells her to calm down, reassuring her that Urahara is trustworthy. She insists that he's probably just come up with another idea and it is nothing for them to be alarmed about.

Descent into the Nest of Maggots
Outside the Second Division land, Urahara and Hiyori wait for the doors to open. Hiyori steadfastly refuses to enter the compound, despite Urahara's patient coaxing. He is soon forced to grab her by the back of her shirt and pull her through the doors with him, much to her chagrin as she screams for him to let go of her. As they venture through the trees, it is explained that the Onmitsukidō was originally a separate organization to the Gotei 13. However, when the head of the unit becomes a captain as well, the two units become closely linked. Under Yoruichi's leadership, the commanders of each of the five sections of the Onmitsukidō are seated officers in the Second Division.

Urahara tells Hiyori that as the Second Division's Third Seat, he was the head of the Detention Unit. He explains the main duty of the Detention Unit was guarding those who had committed crimes in Seireitei. Hiyori insists that it means he was a prison guard, but Urahara refutes this, maintaining that his role was quite different as his main role was to imprison and then supervise the prisoners. She initially argues with him, but then notices his use of the "main" and asks what other duties the unit had. Kisuke tells her that he also investigated and detained any Shinigami who was deemed to be a potential threat to other Shinigami or might impede the duties of their Division.

Dangerous people and Shinigami were locked up in a special facility that was held on the grounds of the Second Division. Urahara elaborates to Hiyori that the location of the facility was North-West of the division barracks and is surrounded by a large moat on all sides. He further explains that the facility is also underground and is called the Nest of Maggots. After cross the bridge that goes over the moat, they come upon a large door that is guarded on either side by two members of the Onmitsukidō which serves as the entrance to the facility.

As they descend into the cave, Hiyori asks if people are really locked up in such a place. Urahara replies that it is a horrible affair, but it is not quite a prison. He shows her that while the detainees cannot leave, their movements are not restricted within the facility. When Urahara warns her that someone might suddenly attack her, she asks what they have done. Urahara tells her that they have not actually done anything wrong, but have simply been deemed to be dangerous elements according Seireitei's regulations. Hiyori criticizes this, but is interrupted by Urahara, who asks her if she knew any Shinigami who has withdrawn from the Gotei 13.

Urahara gravely explains that there is no such thing as “withdrawal.” He tells her if somebody has to leave the Gotei 13 due to personal circumstances, it is called a "leave of absence." If that leave of absence prolongs and it is unlikely the person will come back, it results in "Decommissioning." Actual withdrawal from the Gotei 13 of the member’s own volition is not accepted. Instead, “withdrawal” is a cover that means the Shinigami has been forcibly transferred to the Nest of Maggots. This is all in accordance with the views of the Central 46.

Urahara tells Hiyori that he has always had something on his mind ever since he took command of the Detention Unit. He notes that he has thought that even though the people kept in Special Detention are considered possibly dangerous, they might be able to turn their dangerous potential into assets if they were given a suitable environment in which to work. Hiyori is then attacked by a detainee and instinctively reaches for her sword. As she recalls that she did not have her blade, Urahara protects her from the attacker and apologizes for not reminding her that she did not bring her Zanpakutō. He states that the Nest of Maggots forbids bringing any weapons into the facility. As such, all Detention Unit leaders must be capable of subduing any detainee with their bare hands.

After fending off the attacker, the two go down into a lower level. Urahara then shows Hiyori the only detainee that is placed in a cell, who asks him what business he has here. It is then revealed that the prisoner is Mayuri Kurotsuchi. Urahara tells a shackled Kurotsuchi that he has come to offer him the opportunity to leave. Surprised, Hiyori asks who Kurotsuchi is. In response to Hiyori’s manner of speech, he states that she seems to be a boy with no manners. This angers Hiyori, who calls him a “white dango.” Urahara tells Kurotsuchi that Hiyori is his lieutenant, which prompts Kurotsuchi to congratulate Urahara on his promotion. Urahara thanks him, but goes back to the topic of his proposition as Kurotsuchi has not yet given a reply.

Kurotsuchi turns down his offer to leave the Nest of Maggots, and stating that he is satisfied with his life there when asked why by Urahara. When Urahara points out that there is nothing to tinker with in the detention facility, Kurotsuchi asks why he wants to free him. Urahara states that he needs Kurotsuchi's abilities. Suspicious of him, Kurotsuchi suggests Urahara to stop lying. Urahara brushes off the brazen response, noting how much Kurotsuchi is on guard around him. Despite this suspicion, Kurotsuchi points how he still has difficulty understanding Urahara and how Urahara is a truly unpleasant type of man. Urahara again asserts that he genuinely needs Kurotsuchi's skills and reveals that he is thinking of creating an organization within the Twelfth Division unlike any organization seen before in Soul Society called the Research and Development Institute. He goes on, saying that he would like Mayuri to be its vice-president. Hiyori is shocked at this, as Mayuri asks if Urahara wants him to work under him. Kisuke confirms this and replies that it is not a bad deals as if he were to die, the organization would be his to do with as he pleases. Kurotsuchi smiles, saying that Urahara truly is an unpleasant sort of man.

Contest between Shunpo Masters
Elsewhere, at the Kuchiki Manor, a teenage Byakuya Kuchiki is practicing his Zanjutsu skills with a wooden sword. His grandfather, Captain Ginrei Kuchiki of the Sixth Division, arrives on the scene and compliments his grandson after observing some of his technique, noticing how hard he is working. Byakuya is please to see Ginrei and asks him if he is staying at home for the rest of the day or returning to his division barracks for some work. Ginrei confirms that he is staying for now and advises Byakuya to leave his training for a while as he has a visitor.

The visitor turns out to be Yoruichi, who immediately begins to tease the young trainee by pushing her breast into the side of his head. Byakuya reacts angrily and swings his weapon in her direction, calling her a "demon-cat". Yoruichi easily evades the swipe and mocks his method of greeting her. Byakuya insists as the heir to his clan, he does not need to care about the likes of her. In response, Yoruichi steals the tie from his hair and challenges him to try and retrieve it from a mere girl. Byakuya uses Shunpo to chase her, claiming his is now faster than her technique, leaving Ginrei alone in the garden. The captain wonders to himself when his heir will rid himself of his rash attitude before going to make himself some tea.

The New Lieutenant of the 13th Division and the New 5th Division Officer
Elsewhere, Kaien Shiba is having tea with Captain Jūshirō Ukitake. He repeats to Ukitake that he does not wish to be a lieutenant. Ukitake only smiles, telling him to not say that since he will just disappoint him again. In response, Kaien saying that there are others who deserve to be promoted ahead of him. Noting how Kaien's attitude is appears to be out of a sense of duty, Ukitake states this is very much like him. Disappointed with his reply, Ukitake turns the conversation to the latest genius to graduate from the Shin'ō Academy since Kaien himself. He says that this boy completed the academy course in just one year. Kaien states that this is quite impressive as Ukitake states that the boy is the same age as Byakuya. Ukitake tells Kaien that he heard the child had a seated officer position reserved for him before he joined the Gotei 13.

Trying to act modest, Kaien uses this to try to further support his wish to not be promoted to lieutenant. Kaien then asks what division the young genius was assigned to, Ukitake replies that he is now part of the Fifth Division. Later that evening, Sōsuke Aizen applauds the young Gin Ichimaru's skills. It is revealed that Gin killed his division's Third Seat. Aizen then asks Gin how did he find the Fifth Division's Third Seat. Gin simply states that the dead Shinigami was not worth his time, to which Aizen replies he is glad to hear that.

Aftermath
The history of several Shinigami is revealed. Urahara is successfully able to recruit Mayuri Kurotsuchi to be his Third Seat and Vice President of the Shinigami Research and Development Institute as part of his work as the captain of the Twelfth Division. Urahara is also able to establish said organization. Ukitake tries to recruit Kaien Shiba to be the lieutenant of the Thirteenth Division. Gin Ichimaru joins the Fifth Division of the Gotei 13 and is recruited by Sōsuke Aizen.