So I thought long about it (7 hours) and it occurred to me that the person Sasuke may be talking about is SO6P. Listen. The scroll that Sasuke is looking at looks like a summoning scroll.
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Imagine that the scroll belonged to the So6p. We know that it's a blood contract between the user and animal. Blood=DNA
Which means the So6p could be brought back with Edo Tensei. He knows the answers to the questions Sasuke is asking. He who create ninjutsu thus create the "shinobi". He whose sons began the Senju and Uchiha " clan". It could explain why Sasuke is seeking Oro because there are few who know the secrets to Edo Tensei . He cannot release Kabuto so who else knows?!
My other thought would be Madara. Sasuke seems shocked when Juugo told him "Edo " Madara was still in the land of the living . It's simply because he believed Tobi was Madara. The person who knows every answer may be him. As a Uchiha clan Elder , as a founder of the village system . I'm excited to find out.
