Kisuke Urahara Infiltrates the S.R.D.I.

 is an event that took place during the Reigai Uprising, involving Kisuke Urahara and Ichigo Kurosaki sneaking into Soul Society to gain access to Kagerōza Inaba's labs at the Shinigami Research and Development Institute.

Prelude
As Ichigo and Urahara prepare to leave for Soul Society, Ishida asks Ichigo one more time if he is sure that he wants do this. Ichigo tells him to forget it as they do not have the time to worry. Urahara agrees, saying that while restoring Ichigo's Reiatsu is a huge gamble, succeeding is their only hope. Before they can go, Kon demands to accompany them. He insists that he will help save Nozomi Kujō, despite being a body that would make it difficult for him to assist. Ichigo agrees and the others give him words of encouragement. Urahara then asks them a favor.

In Soul Society, Inaba checks upon Nozomi, having captured her and bringing her to his lab. An alarm then sounds and Reigai-Nanao Ise informs him that they have detected several Reiatsu signatures in the Dangai. He asks if it is “them”, which she confirms. She states that she will send forces to the Senkaimon immediately. At the Senkaimon, the Reigai begin to gather in preparation for the arrival of the intruders. Reigai-Tōshirō Hitsugaya comments that something is off as he cannot sense them coming. Reigai-Kenpachi Zaraki then rushes into the Senkaimon, saying that it is foolish to simply wait for them. He is quickly followed by Reigai-Hitsugaya. There, they find Lieutenant Renji Abarai, Rukia Kuchiki, Uryū Ishida, Yasutora Sado, and Orihime Inoue waiting for them. Reigai-Kenpachi quickly comes at Renji. However, Reigai-Hitsugaya soon discerns what is going on. Renji recalls Urahara's request that they act as a decoys.

This then allowed the powerless Ichigo and Urahara, wearing his Reiatsu concealing cloak, to sneak in to Soul Society via the natural Senkaimon that Nozomi previously revealed.

Reigai-Hitsugaya realizes that they are decoys and tells Reigai-Kenpachi to return to Seireitei, which he reluctantly does. Rukia stops Renji from pursuing them, insisting that they fall back. Sado says that they now have to trust in Ichigo, Kon and Urahara. Upon arriving in the Seireitei, Urahara locates an entrance to the underground tunnel network.

Inside the S.R.D.I.
At his lab, Inaba removes his flamboyant attire in preparation for the fusion. He tells Reigai-Nanao Ise to begin, but she wonders if he is certain that he wishes to proceed in his current condition. He states that he is aware that the fusion might not be stable, but that he should be able to manage this by using medication. He steps into the glass chamber next to the one holding Nozomi, and tells Reigai-Nanao and Reigai-Nemu Kurotsuchi that he is counting on them.

At the S.R.D.I., Urahara, Ichigo and Kon sneak inside. However, they find the facility used by Inaba to be empty. Ichigo wonder what is going on. Urahara tries to calm Ichigo, saying that while he too is worried about Nozomi, they should proceed with what can do at the moment. As such, they will begin by restoring Ichigo's powers. While he sets about doing so, Kon wonders why the equipment is for making Gikongan. Urahara explains to Kon and Ichigo that Inaba camouflaged his Reigai-making equipment in the S.R.D.I. so that it would appear as if he had been conducting legitimate research. He then details how he will restore the Reishi data Ichigo collected from the Dangai in the form of a Modified Soul which he will fuse with Ichigo's soul. He warns that there will be great strain on his soul as he is not a Reigai, but Ichigo replies that he accepts the risk.

Urahara then proceeds to hacking into Inaba's records for his Mod-Soul creation data. However, Reigai-Nemu detects something possibly occurring with the machine at Inaba's lab and goes to investigate. But before she can properly check, Reigai-Nanao tells her that the fusion is having an issue. She tells Reigai-Nemu to go check on the fusion's status on her end. She complies, allowing for Urahara to fully gain access to the Mod-Soul data. As the Mod-Soul is created, Ichigo brings up that he thought Inaba was unable to reproduce his Hollow powers. Urahara confirms this, explaining that they are simply extracting the power from Ichigo's own Reishi and copying it to a Mod-Soul. Thus, he can restore Ichigo's Reiryoku, but not his Hollow powers. Before the Mod-Soul can be completed, an alarm goes off. Urahara states that the enemy is on to them. There is then an explosion from the equipment.

At his lab, Inaba remembers Ōko Yushima's induction into the Gotei 13, reassignment from the 10th Division to the 12th Division, the development and shutting down of Operation Spearhead and Yushima's hiding of the development information in the Dangai and final act in the 12th Division, requesting that the Mod-Souls created from his Reishi hide among the Shinigami and one day complete his research as he is left in a catatonic state.

As the dust clears away, Urahara finds Ichigo among the rubble and explains that Inaba had foreseen their plan. Ichigo states that his powers have returned and reveals that he grabbed the Modified Soul before the explosion. After finding Kon, they move to leave to avoid being found. Ichigo collapses and one eye turns black. Urahara tells him that the Mod-Soul was incomplete and as a result his powers are highly unstable so his Hollow powers could go out of control and take over him. Urahara deduces that while Inaba's main objective is to fuse with Nozomi, Inaba would not simply sacrifice all his research as a scientist. As such, Inaba must have another lab elsewhere. As Ichigo returns to normal, they are found by some Shinigami. They quickly defeat the newcomers and go in search of Inaba's lab and Nozomi.

However, they are found by the Reigai doubles of the Gotei 13 captains. Urahara tells Ichigo and Kon to flee as he tries to hold them off, but then Yoruichi Shihōin and the Gotei 13 captains arrive ready to fight the Reigai.

Yoruichi explains that she had sent word to Kūkaku Shiba about the situation and she arrived with Jidanbō Ikkanzaka and Ganju Shiba to assist the captains in their fight with Inaba. Thanks to her help, they were able to retreat. They then healed their injuries at Kūkaku's home and waited for an opportunity to strike back. Captain Kenpachi Zaraki then attacks the Reigai and tells Ichigo, Urahara and Kon to get out of the way. Yoruichi tells the trio to leave the Reigai to them and they leave. The captains begin to take on the Reigai.

Researching the Past
Ichigo sluggishly follows Urahara and Kon until he collapses, his eyes having begun to turn black. He awakens in a warehouse where he is told by Kon that he nearly turned into a Hollow again. Urahara explains that the balance between his Hollow and Shinigami powers is breaking down and reluctantly asks him to remain there. Kon tries to be supportive, saying that he will restore Ichigo's Shinigami powers. After Ichigo remembering Kon's words before they left the Human World, he tells Kon that he is counting on him and hands him the Reishi collector. Urahara binds Ichigo with Kidō and they leave him. When Kon asks if it was necessary, Urahara states that it is just to be a precaution, but that he is uncertain if it will help.

As the captains battle the Reigai at the S.R.D.I., Kon angrily asks Urahara why they are at the back door of the S.R.D.I. when they had just fled from there. Urahara explains that he was trying to throw the enemy off their trail and states that he wants to investigate the 12th Division, Inaba's unit. As they go through the building, he mentions that there is little left from his time as captain of the Division. This surprises Kon, who thinks this means that he knew about Inaba. Urahara tells him that Inaba had not joined the Division when he was still in the Gotei 13. He then succeeds in gaining access to the computer records and learns that Inaba joined the Gotei 13 sixty years ago. Kon asks if there is any record on Nozomi, which Urahara answers that there isn't. This then prompts him to check another thing before he tells Kon to come along to a library. There, Urahara checks the records of each Division's recruits and discharges between his exile and Inaba's first appearance. He makes a discovery and tells Kon that they will head to the 10th Division barracks, with Kon complaining about Urahara's secretiveness.

As Kon and Urahara evade Shinigami patrols, Kon demands to know what Urahara learned. Urahara reminds Kon about Nozomi's and Inaba's differing accounts of their origins. He explains about his theory on the two's accounts both being correct by the possibility that Inaba is also a Mod-Soul. This would mean that they were both once part of another Mod-Soul. Urahara then poses the question on who made the Mod-Soul that Inaba and Nozomi came from. Urahara surmises that the two must both be Mod-Souls based on the true Mod-Soul developer since Mod-Souls are originally created from the Reishi of a Shinigami and then enhanced. Thus, Nozomi and Inaba are both the first Mod-Soul and the Mod-Soul developer. He tells Kon that by finding this developer, they will likely find the laboratory as well. He states that he had been investigating this theory by searching for evidence of a Shinigami who disappeared prior to Inaba's arrival, but the 12th Division records had been erased and in the library, he found evidence of the information in the 10th Division's records from ninety-six years ago being altered.

Upon making further investigation of the unaltered records at the 10th Division's barracks, Urahara finds the record of Ōko Yushima. As they look at the record, Kon wonders what the cross mark means. Urahara states that it means Yushima does not exist in the 12th Division and concludes from the record that he is in the Nest of Maggots.

At the Nest of Maggots
As Kon and Urahara go through the Nest of Maggots, Urahara explains how the Gotei 13 have no provision for resignation. Thus, if no records exist for a Shinigami after their time in service, they can only be at the Nest of Maggots. They are then confronted by Reigai-Suì-Fēng and Reigai-Marechiyo Ōmaeda. Urahara asks Kon to sneak in, while he holds them off. Reigai-Suì-Fēng then orders Reigai-Ōmaeda to go after Kon. Urahara then tells Reigai-Suì-Fēng that he correctly deducted that Ōko Yushima, the developer of Mod-Souls, is at the Nest of Maggots.

Irritated that Urahara figured out Yushima's location, Reigai-Suì-Fēng releases her Shikai and charges at Urahara. Kon is then forced to run towards Urahara as Reigai-Ōmaeda chases him, crying out for help. As Urahara is seemingly struck by Reigai-Suì-Fēng, his body explodes as it is revealed that Reigai-Suì-Fēng attacked a Portable Gigai. Kon continues running and quickly leads Reigai-Ōmaeda to crash into Reigai-Suì-Fēng. Urahara then finishes the battle by using his Shibari and Hiasobi techniques for his Juzutsunagi attack. The two compliment each other on a good job with their “doppelganger plan.”

Aftermath
After defeating the Reigai, Urahara and Kon go in to check the facility's cells. They then find Yushima slumped in a chair in a cell. They go into the cell and As Kon tries to wake him, Urahara notes that it does not look like he will ever regain consciousness. Meanwhile, Ichigo escapes from his restraints and becomes a Hollow.