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How did Minato cut the tree? Branches of the Tree that is 100 times bigger than Hashirama's.
Well, the databook says that Minato has futon. Kakashi said that Minato tried to put his nature chakra in the rasengan meaning he already knew a element and he knew how to use it without seal.
The more possible answer is this jutsu but with wind:
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Being logical this must have been. He cant summon, Katon would have burn the people, lighting doesnt make sense. Rasengan nethier so only wind Jutsus.