Who could it Possibly be!?

[itachi izanami]

The Man standing behind Sasuke?

 

[Yanks]

You're kind of asking like we actually know the answer, which we don't.
OT, Kabuto

 

[Lady Tsunade Sama]

Jiraya ... hmm it is possible

 

[ChiefHermit]

rikudo
phosttooshort

 

[TheKyuubiIchigo]

White Zetsu...

Need proof?
Check this theory out! :

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[Gary777]

Does the zetsu want to steal his eyes

 

[Smirk]

I still think its Lady Gaga but some believe its Kabuto, or some really hyped up enthusiast think its s06p or izuna

 

[Xāvî1]

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Any one of them