Only when a fixed combination reliably produced a fixed result could it become "common knowledge" accepted throughout the ninja world.
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For example, Kakashi Hatake and the others had stated with certainty that wind + water = Ice Release, while water + earth = Wood Release.
Of course, during the Fourth War, when Impure World Minato saw Sasuke's Blaze Release: Kagutsuchi combined with Naruto's Wind Release: Rasengan, he had immediately blurted out "Scorch Release."
Wu Yu had now personally confirmed this by combining Water Release and Earth Release into Wood Release—though it was merely a piece of uncontrollable rotten wood.
At the same time, he confirmed something else: this was indeed extremely difficult.
Given Wu Yu's Chakra control, he estimated that his [Seal Proficiency] was even stronger than when it had previously been rated at 8, putting it roughly at Seal Proficiency 9—yet even with such high-level Chakra control, merely merging the two simplest and most fundamental forms of Water Release and Earth Release required the utmost care in order to successfully fuse those mutually conflicting Chakras.
Since water + earth could undeniably produce Wood Release, even if it was not flexible Wood Release Chakra but an actual Wood Release Technique, Wu Yu believed that Konoha's ninja must have conducted plenty of experiments on it.
Konoha certainly had no shortage of Water Release users or Earth Release users.
But in terms of the precision of Chakra control and the tacit coordination between partners, how many pairs could match Wu Yu and Shadow Wu Yu, who were one mind in two bodies, or Sasuke and Naruto during the Fourth War?
So perhaps Wood Release having been lost for so many years really had simply been a matter of luck—
Wu Yu thought to himself, First, people from other villages might not