Something has been bothering me about Edo Tensei. Or atleast, what the anime showed of Edo Tensei when Orochimaru showed it. In the anime he summoned the 1st and 2nd. Sarutobi stopped the 3rd casket from being completely summoned, but you could clearly see the symbol for the 4th on the cover of it. Sarutobi then goes on to use a sealing technique on Oro/1st/2nd, which the 4th used on the kyuubi to seal it in Naruto. Sorutobi also explained that using that technique also seals the sealer's soul inside the shinigami's stomach along with whoever it is being used on. So, how did the anime have the 4th being summoned if his soul was sealed away? There is also a big clusterfuck on how the 4th sealed the kyuubi in Naruto using that technique along with the Eight Trigrams Sealing Style.
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