Itachi is a plot no jutsu.
Seriously, the way Kishi uses Itachi is more akin to a plot device, rather than an independent character.
Specifics:
His relationship with Sasuke. Sasuke's entire character is defined by something Itachi has done to him, said to him or inspired to do.
Sasuke wanted to seek power by any means necessary because of Itachi.
Sasuke wanted to kill Danzo and destroy the Leaf Village, because of what happened to Itachi.
Sasuke decides to revive Orochimaru, who revives the Edo Hokage and elects to go join the Shinobi Alliance. Because of the truth Itachi showed him before he passed away a 2nd time.
Sasuke announces he wants to be Hokage to the K11, and thinks of Itachi after Madara stabs him in the chest. Saying he can't die yet.
Sasuke announces that he will execute the Gokage, Naruto and all the tailed beasts and appoint himself as Hokage. He tells Naruto that Itachi was the "True Hokage" and that Sasuke's revolution will change the Shinobi World.
Shin Jr and Shin Sr both wanted to kill Sasuke because he killed Itachi. Apparently, Shin was an admirer of Itachi and wants revenge on Sasuke.
Then there are the things Itachi does, which function more as plot executed through the writer, than as logical conclusions a character in Itachi's position would make.
Example:
The Sasuke vs Itachi fight.
A. Specifically Itachi sealing Orochimaru and removing the curse mark from Sasuke.
Two things.
1. How did Itachi know Orochimaru was absorbed by Sasuke? The only people who knew exactly what happened were Oro, Kabuto (via genjutsu from Sasuke) and Sasuke himself. This is knowledge a character in Itachi's position could not have had. But Kishi uses specific language to indicate that Itachi was, somehow aware of this happening, and was waiting for it.
2. Itachi wanted to remove the curse mark from Sasuke. Obito says that was his intention during their (Sasuke and ItachI), but again, how could Itachi know the curse mark was dangerous? There are any survivors from the curse mark who weren't presently living with Orochimaru or at one of his bases. This means there was no one to tell Itachi about the corrosive and damaging effects of using the seal; as relayed to Sasuke and to us by Sakon.
Both of these seem more like Kishi wanting to kill two birds with one stone via Itachi. He was done with the curse mark and Orochimaru for the time being and wanted them out of the way. Which Itachi (plot) facilitated via the totsuka blade.
However, that opens up another can of worms, with regards to the totsuka blade itself.
B. We are told anything the totsuka blade pierces is sealed inside the sake jar of Itachi's susanno, which is also equipped with the yata mirror; an item said to repel all attacks. So with weapons that powerful, why does Itachi only use it when plot requires him too? E.g. against Oro and against Edo Nagato. Why didn't he use his spirit weapons and susanno to fight the Akatsuki?
If we accept that Itachi was in the dark about Obito's true goal, or reviving the Juubi and carrying out the Moon's Eye plan. We can't ignore that Pein/Nagato was very clear about what he wanted the tailed beasts for. War. Nagato's plan if you recall, was to gather all 9 tailed beasts and unleash them on every village in the NV. Causing massive damage and high casualties. After awhile, when Nagato believed that people had suffered enough, he would cage the beasts and make the world in his own image.
Now, Itachi is a pacifist and slaughtered his own clan just to avoid a civil war between Konoha and the Uchiha, and yet he silently goes along with Nagato's mad plan for a world war? If the hype around Yata and Totsuka are to believed, Itachi could've made a fight with the Akatsuki to prevent this, but he doesn't. Totsuka is only used when the plot demanded it and Itachi wasn't well enough to make a difference. Had Naruto not pulled a surprise victory against Pein and talk no jutsu'd Nagato to suicide, things would've been worse to the NV.
C. The last thing Itachi does, that facilitates more of a plot role than a character role, is his use of Izanami on Kabuto in order to end the Edo Tensei. It's just too perfect that there would be ANOTHER OP sharingan genjutsu that can affect a person regardless if their 5 senses are activated or not. And it's just too perfect that Itachi, not only knows what this jutsu is but how to use it and explains it to Sasuke how it works. This despite, Itachi never using the jutsu before.
It's like Kishi didn't know how to end the Edo Tensei without killing Kabuto or writing a way for Sasuke to survive the fight with Kabuto, so he uses Itachi (plot) as a way to facilitate what he wants to happen. Again!!!
Seriously, the way Kishi uses Itachi is more akin to a plot device, rather than an independent character.
Specifics:
His relationship with Sasuke. Sasuke's entire character is defined by something Itachi has done to him, said to him or inspired to do.
Sasuke wanted to seek power by any means necessary because of Itachi.
Sasuke wanted to kill Danzo and destroy the Leaf Village, because of what happened to Itachi.
Sasuke decides to revive Orochimaru, who revives the Edo Hokage and elects to go join the Shinobi Alliance. Because of the truth Itachi showed him before he passed away a 2nd time.
Sasuke announces he wants to be Hokage to the K11, and thinks of Itachi after Madara stabs him in the chest. Saying he can't die yet.
Sasuke announces that he will execute the Gokage, Naruto and all the tailed beasts and appoint himself as Hokage. He tells Naruto that Itachi was the "True Hokage" and that Sasuke's revolution will change the Shinobi World.
Shin Jr and Shin Sr both wanted to kill Sasuke because he killed Itachi. Apparently, Shin was an admirer of Itachi and wants revenge on Sasuke.
Then there are the things Itachi does, which function more as plot executed through the writer, than as logical conclusions a character in Itachi's position would make.
Example:
The Sasuke vs Itachi fight.
A. Specifically Itachi sealing Orochimaru and removing the curse mark from Sasuke.
Two things.
1. How did Itachi know Orochimaru was absorbed by Sasuke? The only people who knew exactly what happened were Oro, Kabuto (via genjutsu from Sasuke) and Sasuke himself. This is knowledge a character in Itachi's position could not have had. But Kishi uses specific language to indicate that Itachi was, somehow aware of this happening, and was waiting for it.
2. Itachi wanted to remove the curse mark from Sasuke. Obito says that was his intention during their (Sasuke and ItachI), but again, how could Itachi know the curse mark was dangerous? There are any survivors from the curse mark who weren't presently living with Orochimaru or at one of his bases. This means there was no one to tell Itachi about the corrosive and damaging effects of using the seal; as relayed to Sasuke and to us by Sakon.
Both of these seem more like Kishi wanting to kill two birds with one stone via Itachi. He was done with the curse mark and Orochimaru for the time being and wanted them out of the way. Which Itachi (plot) facilitated via the totsuka blade.
However, that opens up another can of worms, with regards to the totsuka blade itself.
B. We are told anything the totsuka blade pierces is sealed inside the sake jar of Itachi's susanno, which is also equipped with the yata mirror; an item said to repel all attacks. So with weapons that powerful, why does Itachi only use it when plot requires him too? E.g. against Oro and against Edo Nagato. Why didn't he use his spirit weapons and susanno to fight the Akatsuki?
If we accept that Itachi was in the dark about Obito's true goal, or reviving the Juubi and carrying out the Moon's Eye plan. We can't ignore that Pein/Nagato was very clear about what he wanted the tailed beasts for. War. Nagato's plan if you recall, was to gather all 9 tailed beasts and unleash them on every village in the NV. Causing massive damage and high casualties. After awhile, when Nagato believed that people had suffered enough, he would cage the beasts and make the world in his own image.
Now, Itachi is a pacifist and slaughtered his own clan just to avoid a civil war between Konoha and the Uchiha, and yet he silently goes along with Nagato's mad plan for a world war? If the hype around Yata and Totsuka are to believed, Itachi could've made a fight with the Akatsuki to prevent this, but he doesn't. Totsuka is only used when the plot demanded it and Itachi wasn't well enough to make a difference. Had Naruto not pulled a surprise victory against Pein and talk no jutsu'd Nagato to suicide, things would've been worse to the NV.
C. The last thing Itachi does, that facilitates more of a plot role than a character role, is his use of Izanami on Kabuto in order to end the Edo Tensei. It's just too perfect that there would be ANOTHER OP sharingan genjutsu that can affect a person regardless if their 5 senses are activated or not. And it's just too perfect that Itachi, not only knows what this jutsu is but how to use it and explains it to Sasuke how it works. This despite, Itachi never using the jutsu before.
It's like Kishi didn't know how to end the Edo Tensei without killing Kabuto or writing a way for Sasuke to survive the fight with Kabuto, so he uses Itachi (plot) as a way to facilitate what he wants to happen. Again!!!