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

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.

Prologue
As Ichigo Kurosaki and Kisuke Urahara prepare to leave for Soul Society, Kon demands to accompany them, insisting that he will help save Nozomi. Ichigo agrees and the others give him words of encouragement. Kisuke then asks them a favor.

In Soul Society, in Inaba's lab, an alarm sounds and the Reigai-Nanao Ise informs Kagerōza Inaba that they have detected several reiatsu signatures in the Dangai. 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. At the Senkaimon, Reigai-Tōshirō Hitsugaya comments that he cannot sense them coming and Reigai-Kenpachi Zaraki rushes into the Senkaimon, quickly followed by the Reigai-Hitsugaya. There they find Lieutenant Renji Abarai, Rukia Kuchiki, Uryū Ishida, Yasutora Sado and Orihime Inoue waiting for them. Renji remembers Urahara's favor: to act as a decoy while the powerless Ichigo and Urahara, wearing his reiatsu concealing cloak, sneak in to Soul Society via the natural Senkaimon that Nozomi Kujō 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.
Inaba tells Reigai-Nanao to begin, but she asks if he is certain he wishes to proceed given his 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.

Urahara, Ichigo and Kon sneak inside the S.R.D.I. but find the facility used by Inaba to be empty. Urahara tries to calm Ichigo and says that the should restore Ichigo's powers. While he sets about doing so, he 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.

As Urahara hacks into the records of Inaba, the Reigai overseeing Inaba's fusion with Nozomi notice a problem with the fusion. Urahara explains that he can restore Ichigo's Reiryoku, but not his Hollow powers. An alarm goes off and Urahara states that the enemy is on to them. There is then an explosion.

Inaba remembers ‎Okō 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 he hide and one day complete his research as he is left in a catatonic state.

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 begin to leave to avoid being found. Ichigo collapses and one eye turns black. Urahara tells him that the Mod-Soul was incomplete and thus his powers are highly unstable and that his Hollow powers could take over him. Urahara deduces that Inaba must have another lab elsewhere, as a scientist would not sacrifice all his data like that. 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 of the 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. They then healed their injuries at Kūkaku's home and waited for an opportunity to strike back. Kenpachi Zaraki 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 to be safe, but that he is uncertain if it will help.

At the S.R.D.I., as the captains battle the Reigai, 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. He mentions that there is little left from his time as captain of the Division, which 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. They then go to a library where Urahara checks the records of each Division's recruits and discharges between his exile and Inaba's first appearance. They then head to the 10th Division, with Kon complaining about Urahara's secretiveness.

Kon and Urahara evade Shinigami patrols. Urahara reminds Kon about Nozomi's and Inaba's differing accounts of their origins. He explains that they were both a single Mod Soul based on the developer of the Mod Souls. He explains that he had been 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 96 years ago being altered. Urahara finds the record of Yushima and concludes from the record that he is in the Nest of Maggots.

Aftermath
There, they are confronted with two Reigai. After defeating the Reigai, Urahara and Kon find Yushima slumped in a chair in a cell. As Kon tries to wake him, Urahara notes that he may never regain consciousness. Meanwhile, Ichigo escapes from his restraints and becomes a Hollow.