Inaba, while working with other 12th Division members, wears a standard uniform, which is a laboratory coat over the standard Shinigami shihakushō. He is quite tall and thin. He has chin-length straight hair which parts on the left side of his head. The right side of his hair is green, and the left is yellow. He has a somewhat long face with circular glasses, and wears white gloves.
When not with others, he wears a long yellow robe which buttons up in the front and protrudes upwards from the neck, covering the entirety of the back of his head. He does not wear glasses, wears gloves, and carries a cane. Inaba's flamboyant attire bears a strong resemblance to that of Mayuri Kurotsuchi's, as noted by Uryū Ishida. 
While he is working with other 12th Division members, he is polite, and obeys orders given by higher-ranked members. When pursuing Nozomi, he is rude to Kon, and heartlessly strikes the girl's abdomen. He has a profound respect for Mayuri Kurotsuchi, though this respect extends to Inaba believing he is superior in all aspects to him. Despite this, he seems to care about Nozomi to some degree. He implores her to get out of the way of his attack, as she might die. After the attack, he claims he is relieved that she is okay. He has a strong contempt for those who forbade “his” research into Mod-Soul science, especially the members of Central 46, whom he deems were "afraid of his research".  As stated by Nozomi, Inaba's being is filled with rage and ambition from Yushima.
Ninety six years ago, a Shinigami named Ōko Yushima invented the Mod-Souls. They were created for "Project Spearhead", which was designed to have Mod-Souls fight against Hollows by placing them in the dead bodies of humans. The project was terminated, due to “moral concerns.” In reality, Central 46 canceled the project, having deemed the ability to freely control the Mod-Souls a possible threat. When everything was to be destroyed, Yushima converted all the information into special Reishi and tossed it into the Dangai, before using some of his own Reishi as a basis to create another Mod-Soul. By unknown means, the Mod-Soul split in two, creating Inaba and Nozomi Kujō. Inaba inherited much of Yushima's memories, and followed suit in fulfilling Yushima's wish to one day complete his research while hiding among the Shinigami. Following Yushima's final orders before putting himself in a catatonic state, Inaba hid himself among the Shinigami, working his way up to the position of 7th Seat in the 12th Division. During this time, he researched the Dangai as a cover for finding a way to retrieve the Mod-Soul data from the Kōtotsu, and created the Reigai.
Gotei 13 Invading Army arc (anime only)
Note: Events occurring in this arc are only in the anime and do not constitute canon material.
In the Research Institute, Akon requests a record of traffic through the Dangai from Inaba. He brings the record book to Akon, who is discussing Lieutenants Nanao Ise's and Rangiku Matsumoto's whereabouts with their respective captains. Inaba reveals there is no indication the two returned through the Dangai. Later, while Akon and Hiyosu are reading a message sent by Rukia Kuchiki, Inaba enters the room. Akon, telling him Captain Byakuya Kuchiki and the others are about to enter the Dangai to conduct a survey, instructs Inaba to show them the way, who acknowledges the order. Before he leaves, seeing the message and the image of an unconscious Nozomi Kujō, he grins.
Inaba enters his facility, filled with a number of Reigai and changes of clothes. He removes his glasses, puts on a new set of gloves and a large yellow robe, and grabs his cane. He uses his cane to move the Reigais of Izuru Kira and Nanao away from the door. Thanking them for waiting, he asks if they shall go. Inaba arrives at Ichigo Kurosaki's house with the two, where Kon has been guarding Nozomi in Ichigo's body. Upon learning of Inaba's presence, Nozomi runs. When she escapes out the window, they pursue her. He knocks out Nozomi when he catches up with her, and binds Kon with Kidō. As he requests his allies kill Kon to finish the job, Uryū Ishida arrives at the scene.
Inaba, evading Uryū's attacks, defeats the Quincy with his Shikai. Turning his attention back to Kon, he realizes that Uryū is still alive, and prepares to kill him. However, Orihime Inoue shields him, and he is attacked by Yasutora Sado. Sado tries to give Inoue time to retreat, but Inaba quickly defeats him. Ichigo shows up, and fights Inaba until the Gotei 13 arrive, at which point Inaba retreats via a Senkaimon. When he returns to his lair, he declares that they will get Nozomi back using their invading army.
The next day, Inaba meets with his Reigai Invasion Force to discuss their plans, where Reigai-Hitsugaya asks him what their next move is. Inaba states that while he has sealed the Dangai and rendered communications impossible, they must formulate a new plan before the Gotei 13 forms a strategy and returns. He notes that a few captains still have not been replaced by Reigai. Reigai-Nanao asks what they shall do with the Captain-Commander, to which he replies that he has something special in store for him. Before leaving, Inaba tells the Reigai that upon Nozomi's capture, their wishes will be fulfilled. Later, Inaba is walking through the Nest of Maggots. Entering the cell of a catatonic green haired man, he rests his lamp on the side table. Chuckling as he grasps the man's head, he states it is useless to run from him. He tries to eliminate Akon when the Shinigami notices something odd in the Dangai records. 
During Captain Retsu Unohana and her lieutenant’s investigation of recent events, Inaba eavesdrops on their conversation for a few moments, and appears before the two when Unohana calls out to him. Kagerōza applauds Unohana's deductive reasoning, admitting her visit to the Daireishokairō was unexpected. Unohana calls upon Isane, and she charges at Inaba, who promptly disappears from the spot. Appearing behind Unohana, he admits to the captain that his abilities came about due to his Dangai research, but are still incomplete. She asks why he separated Soul Society from the planes of existence, to which Inaba replies that they will understand his motives in due time.
Inaba senses the captains' presence as they enter the Dangai, and Unohana questions whether his plans have been foiled due to their intervention. In response, Kagerōza asks if Unohana thought he would allow them to enter without taking action. They discuss Inaba's trap for the captains. As Isane senses the captains successfully enter Soul Society, she notes the absence of Captain Komamura, to which Kagerōza comments that his technology is still far from perfect. He appears to make a move, prompting Isane to fire a Shakkahō spell at him. Inaba disappears as his voice echoes, telling Isane that there is no need to rush, and the two pursue him. Tracking down the scientist, the two confront him inside an underground chamber. Unohana calls on Inaba to stop this madness, stating that his plans will not succeed. She claims killing the Captain-Commander is impossible, going on to say he underestimated the originals' strength, which he refutes. He claims it is hard for him to understand them, primarily due to being disinterested in the affairs of others, and asks whether the same could be said of her, prompting Unohana to ask what he means. As he tells her she will see, Isane raises her sword against her, revealing herself to be a Reigai.
Inaba states he would not face off against a captain of her stature without a plan. He explains to her that he modified the Senkaimon as various Shinigami traveled through it, taking Reishi samples from each Shinigami who used that Senkaimon, created Mod-Souls identical to their original counterparts, placed those Mod-Souls in Reigai, and thus created his invasion force. As Inaba asks whether Unohana is able to understand, a blast door opens, revealing a Reigai of Unohana. Inaba states that he has already sampled her Reishi, thanks to Reigai-Isane, and proceeds to taunt Unohana, asking what her next move will be.
Unohana faces off against her Reigai counterpart with Kidō, escaping as the brief confrontation culminates in a huge explosion. Reigai-Isane flinches from the attack, prompting Inaba to ask about her status. Reigai-Isane answers she is fine, and wonders where the original Unohana escaped to. Kagerōza states she is wise, as she never aimed to fight them from the start, and Reigai-Unohana agrees, explaining the strategic importance of Unohana's move for the Gotei 13. Inaba makes another visit to Yushima. He reassures Yushima, stating that Nozomi will return to Soul Society without fail. As events unfold, Inaba, noticing Ichigo going through the Dangai, makes it so Ichigo meets him in Soul Society. With his Shikai already released, he simply smiles, refusing to answer most of Ichigo's questions, and reveals he is unable to make a Reigai of Ichigo because he is not a pure Shinigami. Trapping Ichigo inside the Dangai, Inaba bids him farewell. Inaba, returning to Yushima, informs him that Komamura's Reiatsu has disappeared, and none of the captains have reached their location. He declares the other Reiatsu sources will also disappear.
As Inaba looks at Yushima, recalling several memories, he notes that things will soon be completed. As Hitsugaya and Kenpachi arrive at the 12th Division’s barracks, Inaba arrives to face them. The two captains question Inaba, who responds by laughing, disappointed they have not realized they have no chance of victory, and releases his Shikai. The two captains, attacking Inaba, initially appear to have the advantage, as Kenpachi seems to overpower Inaba. However, Inaba opens a portal to the Dangai, forcing Kenpachi to pause his onslaught, and Hitsugaya attacks, prompting Inaba to open another portal to defend. Hitsugaya deduces that Inaba's power is to manipulate space. As they continue battling, Inaba begins to reveal the truth about his Zanpakutō; it manipulates all space, and his Shikai can copy and recreate the attacks used on him by his opponents. Kenpachi attacks, but Inaba, recording the attack, sends it back at him. Hitsugaya exchanges strikes with Inaba before trapping his weapon, preventing him from spinning it in the direction for recording.
When Hitsugaya tries to strike, Inaba defends, revealing he can replay events as many times as he wishes. Preparing to finish off Hitsugaya, he is interrupted by the arrival of Captain Suì-Fēng and Isane, who is carrying Akon. As he expresses surprise at their escape, Yoruichi Shihōin arrives to confront him. Realizing she freed the captains he had trapped, Inaba tells her to not underestimate him. She retorts, saying he should not underestimate his adversaries, as more captains arrive. As the Shinigami surround him, Inaba commends them for doing so well against his invasion force, but maintains they will not win. All attack, but several Reigai appear to defend Inaba. The Shinigami engage the Reigai before managing to get to Inaba, whom they seem to successfully cut and defeat. However, his body vanishes, and he reappears to cut all before him. Captain Kuchiki tries to attack him, but the Reigai intervene, and Inaba jumps away to the rafters. As he taunts them, Reigai-Mayuri, who is actually the original Captain Mayuri Kurotsuchi, stabs him from behind, .
Mayuri informs Inaba that he switched places with his Reigai when the Reigai lieutenants appeared in the Human World. Inaba, complimenting his “former captain” on outsmarting him, claims he still has the advantage. Mayuri retaliates, using his Jabarakaina to constrict Inaba, and effortlessly hurls him around before Inaba breaks free. Inaba asks if Mayuri thought he could bind him with such an obvious attack, and the captain simply tells Inaba not to get full of himself, since he was just buying time. Inaba realizes the captain was waiting for Ashisogi Jizō's effect, but states it will not work. Mayuri begins to approach him, and Inaba finds himself unable to move when he starts thinking. Before he can react, Mayuri stabs him. As he holds his wound in confusion, Mayuri states he injected Inaba with a thought inhibitor drug. Reigai-Isane comes to his aid, saying she will heal him. However, Inaba just laughs, admitting his weakness. He kills Reigai-Isane, who unintentionally angers him, and picks up her core from the ash, swallowing it. This forces her into his body and him out of it, no longer affected by the drug. He states this is one way to use Reigai, albeit not perfectly. Appearing behind Mayuri, he forces him back to the ground.
As the Reigai proceed to join their master, Ukitake asks Inaba how he came across the illegal Mod-Soul data hidden in the Dangai. Kyōraku, adding that they will find out eventually, asks Inaba who he truly is. Inaba tells them he created the Mod-Souls and was a part of Project Spearhead. When the project was shut down and everything was to be destroyed, all the information was turned into a special type of Reishi, before being thrown into the Dangai. Inaba addresses Mayuri, stating he agrees with Mayuri's earlier claim that scientists fear oblivion, as he could not let his research be destroyed. Ukitake asks Inaba if this is the reason for Inaba's attempt to resurrect Project Spearhead, and he confirms this, stating his aim is to rule over Soul Society with his invasion force. Inaba thrusts his Zanpakutō into the air, causing the Reigai's Reiatsu-Limiter bracelets to break and their Reiatsu to surge, maniacally explaining that the Reigai were all holding back. As more Reigai arrive, Mayuri notes how Reigai can have any number of spares made, and Inaba finds this laughable, stating Mayuri could never create Reigai of this caliber. As the Shinigami captains are overpowered by his Reigai, he laughs wildly, mocking their predicament. However, he is taken by surprise when a firework is fired at him. Kūkaku Shiba, along with her brother and Jidanbō Ikkanzaka, burst in. He curses and wonders who they are, not having expected others. The Gotei 13 hastily escape as the area fills with smoke.
Afterwards, an injured Inaba awakens from a dream. Visiting Yushima, he asks him why he is worried, telling him everything is going according to plan. He asks if Yushima is worried about Nozomi, saying it is only a matter of time. Coughing up blood, he states he expected to be injured by the originals, as they are not fools. He tells the man he will see to it that the world learns of his wish. Inaba begins restoring the Reigai whose cores were destroyed, and Reigai-Byakuya inquires what he is doing and about Inaba himself. Stating he is recovering well, Inaba instructs the Reigai to tell Reigai-Hitsugaya, Komamura, and Kenpachi they will soon head to the Human World.
During the Reigais' second attempt to retake Nozomi, Reigai-Ukitake, Kyōraku, and Unohana enter the battlefield. They move to battle the Captain-Commander, but Inaba, calling off their attack, appears. Reiterating that he wants Nozomi, he attacks Yamamoto. Ichigo tries to warn Yamamoto of Inaba's powers, but the Captain-Commander states he already knows of them. After briefly strategizing with Ichigo and Yamamoto, Nozomi charges forward to be a decoy. Inaba, slightly confused by Nozomi's actions, dodges, realizing she is trying to use her Zanpakutō's power. Stating that her tactic will not work, he is surprised to see Nozomi, having absorbed Yamamoto's Reiatsu, attack him with Arazome Shigure. Inaba dodges, but is surprised when Yamamoto comes right in front of him to attack. As Inaba defends against Yamamoto's blast, Ichigo comes from behind to strike. Inaba barely survives the assault by having Raikū copy the power of Arazome Shigure to absorb both Ichigo and Yamamoto's attacks. Ichigo, having depleted his Reiryoku, falls from the sky. Inaba proceeds to attack Yamamoto with both copied abilities, but Nozomi gets between the two.
Inaba, voicing his disbelief at Nozomi's attempt to defend Yamamoto, expresses his concern as the Mod-Soul struggles to absorb the force of the attack. Upon seeing her reach her limits, Inaba shouts for her to get away. Nozomi, refusing to give in, continues to try to stop the attack. Seeing Arazome Shigure begin to crack as it absorbs more energy, Inaba begs for Nozomi to stop, as she'll die if she continues. Just as Nozomi looks to give way, Yamamoto intervenes, meeting the blast with one of his own, creating a massive explosion which knocks both the Captain-Commander and Inaba out of the sky.
As Yamamoto faints, Inaba struggles to his feet. He stands and grins maliciously, voicing his relief that Nozomi is alright. As Rukia and Nozomi prepare to fight, Inaba chuckles, telling Nozomi she cannot resist with her broken Zanpakutō. Starting to advance, he is stopped by Renji and Ichigo, who tells Inaba Nozomi doesn't want to come with him, confusing Inaba. Inaba asserts the Mod-Soul research of Nozomi's creator is close to completion, and Ichigo and Kon protest this, saying they will not allow it and Nozomi would never be happy about that. Inaba states what makes him happy should please Nozomi as well. Ichigo tries to argue, but Inaba claims he knows Nozomi best, thus it is impossible for Ichigo to understand Nozomi. Inaba reveals that he and Nozomi were made from the Reishi of a single Shinigami. When Kon presses Nozomi for information, she just falls to her knees, Inaba noting she hasn't forgotten. He reveals that if Nozomi were to fall into his hands, she and Inaba would become one, and she would be their enemy. Inaba asserts that Nozomi tried to keep her distance from everyone, but became attached to those who tried to protect her. He goes on, saying he is Nozomi, and Nozomi is him. He challenges them to ask Nozomi about the truth of his statement.
Ichigo, Rukia, Renji, and Kon attack, but Inaba quickly defeats the four, stepping on Kon's face. He invites Nozomi to join him in going back to the place where they belong which, after a terse moment, Nozomi refuses. Inaba narrows his eyes, calling her decision "unfortunate", and, resolving to take her back by force, advances. Nozomi tries to strike at Inaba, but he catches her wrist, forcing her to drop her broken Zanpakutō. Kon, cursing Inaba, throws a rock which hits him in the back of the head. This distracts Inaba, allowing Nozomi to escape Inaba's grasp. Kon tells Nozomi to escape while he distracts Inaba, but he acts as more of a pest for Inaba. As Kon shouts at Nozomi to run again, she slowly retreats. Inaba finally grabs hold of Kon, stating he is a failure as a Mod-Soul. Hurling Kon underfoot, he contemptuously mangles the Mod-Soul with his foot, resolving to "eliminate him completely from both the World of the Living and Soul Society." Finally forcing Kon's Mod-soul core from his plushy body, Inaba smiles, preparing to destroy him, when Nozomi, blasting him with Hadō #58: Tenran, rescues Kon's pill and body before fleeing. Inaba, attempting to follow, is halted by a blast of fire from a barely conscious Yamamoto. Inaba, angrily declaring he doesn't have time to battle with Yamamoto, uses Shunpo to chase Nozomi.
In the forest where Nozomi flees to, Inaba tries to grab her from behind. Using Kon as a weapon, she smacks him away. As the slope unexpectedly gives out from beneath him, he finds himself sliding away. Later, Nozomi, going back through the forest, runs into Inaba. Ichigo shouts for Nozomi to get down, and Inaba, attempting to use Raikū, finds it is gone. Nozomi gets down, covering her head with her arms, as Ichigo unleashes all his Reiryoku in a powerful Getsuga Tenshō, which obliterates Inaba. Ichigo begins to tell her to come with him, but Inaba finishes with "to where we belong." Both spin around to see Inaba laughing, and Nozomi wonders how he survived. Inaba reveals that when the slope crumbled under his feet, he took the precaution of creating a decoy for his opponents to waste their time dealing with, which was made possible by Raikū's ability to copy Inaba himself. Bidding farewell to Ichigo, he defeats the Substitute Shinigami with a single strike. Knocking out Nozomi with a strike to the back of the neck, Inaba, picking her up, opens a time-space portal with Raikū, vanishing into it just before Kon arrives.
Upon returning to Soul Society, Inaba, suffering from his injuries, makes preparations to fuse with Nozomi. Reigai-Nanao suggests Inaba get treated, but he shoves her away in anger, insisting the fusion between Nozomi and himself be started immediately. He commands the Reigai to make preparations, which Reigai-Nanao complies with. Placing Nozomi into a glass container, he fills it with pink fluid, claiming it is time to begin. Before beginning the process, Reigai-Nanao voices her concern one more time, but Inaba, while acknowledging the potential danger, is convinced that he can control any possible problems with medication. With no more discussion, Inaba, entering a second container, is submerged in the same fluid as Nozomi, delighted his goal will soon be completed. After some time passes, the system, finally completing its preparations, fuses Inaba with Nozomi. This unison resurrects Yushima as a Mod-Soul with the combined powers of Inaba and Nozomi.
Despite restoring Yushima as a very powerful Mod-Soul, Inaba's plans are ultimately stopped. In a final clash against Ichigo, Yushima is defeated. As a result, the fusion cancels out and restores Inaba and Nozomi. As he dies, Inaba wonders if they were possibly mistaken. Nozomi says a few last unheard words to him, and Inaba, making a slight smile, dies and disappears. 
Reigai: He has various Reigai stored in a room. He manufactured Reigai look-alikes of several Shinigami lieutenants and captains, as well as the Reiatsu-limiting bracelets they wear on their forearms. According to Urahara, he made a special Reigai, which he himself wears. The Reigai seals off his Reiatsu, allowing him to enter the Kōtotsu without dying.
Powers and Abilities
Scientist & Inventor: As a member of the Shinigami Research and Development Institute, Inaba has demonstrated remarkable intellect. With his scientific knowledge, he created Reigai duplicates of several high-ranking Shinigami. He is very insightful, quickly understanding a situation for what it is and quickly comprehending the nature behind his opponent's technique. He is an expert on the Dangai.
Modified Spiritual Energy: While officially only a 7th Seat Officer, Inaba has shown considerable spiritual energy, able to compete with Ichigo's Hollow mask-enhanced Bankai (albeit Ichigo's power was greatly weakened). A unique trait of his Mod-Soul nature allows him to completely conceal his Reiatsu, prevent others from detecting him. He can move about freely in the Dangai, even safely passing through the Kōtotsu to regain the Mod-Soul data.
Dangai Manipulation: As a result of his extensive research on the Dangai, Inaba has gained the ability to alter space. He has used this ability to travel from the Human World to Soul Society, and to manipulate the Kōryū and Dangai. According to Kisuke Urahara, however, his abilities do not extend to control over the Kōtotsu.
Hakuda Practitioner: While never used in actual combat, Inaba showed enough skill to knock Nozomi out with a single chop to the neck.
Raikū (來空, Coming Void): In its sealed form, Inaba's Zanpakutō takes the form of a silver cane. The dark blue handle of the cane curves around to meet the shaft.
Shikai: Raikū is released with the command, "Go Mad" (狂え, kurue). When released, a yellowish green light wraps around the cane and transforms it. The cane transforms into a double-headed voulge with red markings on it. Inaba's Zanpakutō controls the Reigai's Reiatsu-Limiter bracelets on their forearms, allowing him to break them at will, creating a surge in their Reiatsu. 
Shikai Special Ability: Raikū has the ability to manipulate space. This is performed by spinning Raikū, which produces a bell-like chime before activating.
Spatial Manipulation: Raikū can create portals which connect to the Dangai. These portals can drag opponents into the Dangai. By twirling Raikū to the right, these portals can negate attacks, recording the information to recreate the space as he desires. This power can extend to various events: an opponent's attack, movements, and even their Zanpakutō's attacks or attributes. Twirling Raikū to the left, Inaba calls forth a portal that manifests the recorded event, which he is capable of doing as many times as he wishes. This ability can only be used from one direction at a time. With constant use, it can be very taxing on Inaba's energy reserves.
Clones: Kagerōza can use his Zanpakutō's recording ability to record himself, thus producing a clone of himself. Unlike when he clones another person's abilities, the recorded version of him can act independently until it is destroyed.
Spacial Displacement: While appearing to freeze time, by using these portals on himself, Kagerōza in reality relocates himself instantly. With no hint towards his new location, Inaba can catch his opponent off-guard.