Itachi's MS visually represented his weakening over time...

[BlacLord™]

When Itachi first gained MS, the design was pretty thick, like this:

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And by the time he fought Sasuke, the design thinned out considerably:

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Anyone agree?

 

[Uchicha Macho]

Maybe or did he use amaterasu in the first picture?

 

[Deadai]

its possible...

 

[Ace of the fire fist]

His eyes look like they're about to explode in the first pic. But it does look like Amaterasu!

 

[Ldude]

Mangaka/animators' styles change over time. :shrug:

 

[BlacLord™]

Maybe or did he use amaterasu in the first picture?

When he uses Amaterasu, the hole in the middle opens..

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[BlacLord™]

His eyes look like they're about to explode in the first pic. But it does look like Amaterasu!

Kisame warned him about overusing it, tut tut.. xd

 

[Ace of the fire fist]

Kisame warned him about overusing it, tut tut.. xd

Yeah, he did. He might of known he would die soon by Sasukes' hands anyway so he thought yolo. He probably played in the pool with Kisame too.

 

[General PSX360]

Amaterasu in the 1st pic. 6ut nice catch tho

 

[TheBrightSide]

I always thought they decided to change the design but perhaps you are right.

 

[BlacLord™]

Just a thought...