Short Summary
A anime only filler arc that takes place after the Deicide Arc. As Ichigo and the Gotei 13 rest after the battle with Aizen. Imposters of the Squad members slip into the ranks of the Gotei 13 and attack their original counterparts. The originals find themselves on guard unable to tell friend from foe as they try to locate the mastermind. In the midst of this, Kon finds a strange girl who may have a connection with the attacks. While Ichigo, wanting to help, finds himself slowly losing his powers.Main Arc
After the fight with Aizen, Ichigo's powers have become unstable, and it's only a matter of time before they vanish completely. So of course, some inconsiderate megalomaniac picks now to try to take over Soul Society. This time, it's a strange scientist with influence over the Dangai, the passage between Soul Society and the World of the Living. He's capable of distorting the time difference so Shinigami passing through appear days after they left, and even shutting off passage to everyone except his allies (how unfair). This happens to a team led by Mayuri Kurotsuchi to investigate the strange occurrences, but they later show up in Soul Society with Ichigo's substitute badge, claiming that Ichigo was behind everything.
Ichigo, of course, only learns about this when he enters the Soul Society with Rukia (losing his substitute badge to the dangai train thingy in the process) and Renji and Ikkaku try to arrest him. Yoruichi bails him out and explains why his friends now have it out for him; they are not actually the real deal. The scientist, later revealed to be Kageroza Inaba, has created Reigai (like Gigai, but for the Soul Society; they're usually used for testing Soul Candy) in the shape of most of Seireitei's named characters, and put mod souls modeled after the originals in them. These Reigai are almost impossible to tell from the real deal, are more aggressive in nature, and are at least as powerful as their originals. They're the titular invading army, and many of them have infiltrated the Gotei 13 by replacing their counterparts. Ichigo and Rukia escape back to the Living World, but Yoruichi remains behind, fighting the Reigai guarding the gate.
Back in the real world, a female Shinigami has, once again, invaded Ichigo's room. Her name is Nozomi Kujo, and Kon found her in a parking lot, naked except for a rag. Unlike Rukia, however, Nozomi is quite anti-social and seems to want nothing more than to escape and run off on her own. Which is a problem, because Inaba desperately wants to capture her. The first time, he's foiled by Uryu, Chad, Ichigo, and the real Dangai investigation team (the ones who returned were actually the Reigai), but Nozomi remains determined to do her own thing, despite Kon's best attempts at befriending her. Her idea is that she'd escape through a natural Senkaimon that led to an empty world where Inaba couldn't follow, but given the number of Reigai ambushes she runs into on the way, you'd think she'd learn to stick to the buddy system.
Back in Seireitei, Ukitake and Kyoraku become suspicious of the goings-on, and investigate. Unohana joins them, and pinpoints Inaba as the mastermind. Unfortunately, they are confronted by their own Reigai, and Reigai!Kyoraku and Ukitake manage to trick and incapacitate their originals, before going on to attack Yamamoto. The real investigation team returns via Urahara's Senkaimon, and battles between the originals and the Reigai erupt all over Soul Society. Ichigo tries to help, but is trapped in the Dangai, before being returned to the Living World by a mysterious figure.
In the living world, Nozomi slowly defrosts. She admits to Ichigo that she is actually a mod soul- the first mod soul, to be precise. She has shinigami powers, but they're dormant until she awakens them in a fight against a hollow. Unfortunately, this doesn't stop Inaba from finally succeeding in capturing Nozomi. Ichigo's powers have been depleted by the battle, preventing him from following. Urahara devises a plan to have Ichigo retrieve a sample of his shinigami power from the Dangai, incidentally saving his past self because of timey-wimey stuff. Urahara then creates a pill that will allow Ichigo to temporarily return to full strength, but his first attempts are incomplete and imbalanced.
While Ichigo rests to deal with his unstable powers, Urahara finds some backstory. Inaba and Nozomi were once the same shinigami- Oko Yushima. Yushima was a member of the 12th division, and the leader of Project Spearhead (the one behind the creation of mod souls). He's currently completely comatose, because he split his soul into two mod souls- Inaba got the darker half, while Nozomi got his restraint. While Yushima was quite weak originally, the purpose of splitting himself into mod souls was to overcome his limits. Inaba, having his memories, dedicated himself to fusing with Nozomi. When he succeeds, Yushima is reborn with both Inaba and Nozomi's powersets.
Ichigo (now hollowfied because of the imbalanced power restore) attacks the revived Yushima, but the power dissipates when he takes an attack meant for Rukia. Yushima's fusion is unstable, and he asks Reigai!Nemu for the stabilizing agent... only to realize that he's not the only one who can pull off the 'replace allies with imposters' trick. "Nemu" was actually Kon, and he both prevents Yushima from permanently stabilizing the fusion and gives Ichigo the complete pill, allowing him to temporarily be back at full strength.
Turns out, without the handicap on their biggest heavy hitter, Ichigo and friends are more than a match for even Yushima. Yushima tries to unleash a doomsday device, but finds that this is the last straw for his Reigai. The Reigai wanted to protect Soul Society in their own way, and sacrifice themselves to destroy it. The decisive blow comes when Nozomi takes control of the fusion and forces Yushima to stab himself, weakening him enough that the fusion splits soon after. Nozomi and Inaba fade away, the former grateful that she was able to save her friends. Ichigo's powers then disappear completely, with just enough time to say one final goodbye to Rukia before he can no longer see her.
Gotei Invasion Army Arc has the following tropes:
- Adaptation Expansion: The end of the arc afterward sees Ichigo's power slowly fading. Thus Rukia and he spend one more day together hanging out before he has to say goodbye to her when he's unable to see her.
- Back from the Dead: A few Reigai get taken down through the arc. But as long as the modsoul is intact, they can be brought back to life.
- Big Bad: Inaba initially but technically it's Yushima whom split his personalities into two with intent for them to join together again.
- Bishōnen Line: Hilariously played with with Omaeda's reigai imposter. It utterly refused to take on his appearance and was modified to look more handsome, much to Omaeda's chagrin.
- Bittersweet Ending: Soul Society is saved but Nozomi, in trying to help the heroes stop Yushmia, dies in the process. She does have a final goodbye with Kon however. This arc also incorporates Ichigo saying goodbye to Rukia as the last of his power fades and he is unable to see her.
- The Fighting Narcissist: Yumichika is unable to fight his Reigai because he finds his double too beautiful to hurt. The Reigai doesn't have the same problem, because he thinks Yumichika would look even more beautiful covered in blood.
- Fusion Dance: It's eventually revealed that Nozomi and Inaba are two halves of Yushima's soul, which he split into two mod souls in an attempt to increase his own power. When Inaba merges with Nozomi, Yushima is reborn.
- Impersonation Gambit: Mayuri gets a solid hit against Inaba by impersonating his own Reigai.
- Heroic Sacrifice / Redemption Equals Death: The Reigai in the climax as it's revealed they only wished to protect the Soul Society their way and do so by sacrificing their lives to stop Yushima's doomsday device.
- Logical Weakness: Matsumoto manages to defeat Reigai!Kira this way, after he's able to use his upgraded version of Wabisuke to disable her zanpakuto before she can release it. She lets him hit a steel rod a couple times and then drops it on Wabisuke. Since the pole now weighs a thousand times what it originally did, it's too heavy for Reigai!Kira to move, allowing Rangiku to escape and release Haineko.
- Man Behind the Man: Inaba is the most obvious antagonist, but it turns out that the real mastermind is Yushima, who created Inaba and Nozomi by splitting himself. Inaba retained most of his memories, and so was the one carrying out his plan.
- Mirror Match: A few of the fights through the arc mixes up fakes against different members of the Gotei 13.
- Psycho Rangers: The Reigai who were made with the intent to replace the Gotei 13 and take their place. Naturally their personalities are much more aggressive then the real Shinigami's.
- Retcon: The arc is based on the reason for why mod souls were created which was revealed in the manga as part of Kon's back story. However, the anime team rewrite Kon's background to create the plot line that lies behind the arc. The anime's decision to create a character who invented the project doesn't contradict the manga which never mentioned who that shinigami was. The manga eventually reveals the creator of Gikon soul technology was Kirio but doesn't explicitly name her as Project Spearhead's creator.
- Spanner in the Works:
- Kon takes Reigai Nemu's place and both prevents Yushima from stabilizing his fusion and gets Ichigo his full powers back.
- Earlier, Mayuri impersonates his Reigai and lands a solid hit on Inaba, which is what causes the fusion to be unstable in the first place.
- Spot the Imposter: The Reigai initially had a bracelet on their arm to tell whose friend and foe. However they remove it midway through the arc, leaving the only way to tell whose a Reigai by the purple glow in reigai eyes.
- Worf Had the Flu: Ichigo's ability to fight, let alone win, is extremely restricted because his powers are slowly draining after his fight with Aizen.
- You Can't Thwart Stage One: Inaba succeeds in fusing with Nozomi, and the final fight is against their fused form, Yushima.
