Kimiko:
"Counterpoint: Madara."
She says to Ichika
"Madara got so strong as to fight him to stand stills and ties. The difference in power was slight, negligible and unquantifiable. Yet many of his values ran counter to Hashirama's. He was a conqueror, he lived longer, many speculate always would because Hashirama while he had a legendary regeneration ability, modern medical jutsu science has proven such abilities tend to shorten lifespans. We never really got confirmation of what killed Hashirama, he never succumbed to any assassin yet he died early and Madara stepped up to rule in his stead. He might've just succumbed to an early natural death just because his own reliance on his natural regeneration while Madara had more decades to improve beyond what he was when he fought Hashirama. And while Madara according to legend had the nine-tailed fox under his control, Wood Release's entire thing is that Hashirama, according to legend could suppress tailed beast chakra somehow. Meaning its entirely possible that they were canceling each other out in those fights. they probably decided to just stop fighting and be at peace because neither could dominate over the other and were so tired of fighting over their philosophy-whatevers that they just decided to set their differences aside to just make it work rather than dig in on questions that can't be answered or petty differences of method.

Furthermore Yin chakra is only half the equation, the other half is Yang and Hashirama was probably blessed with an unusual amount of that. There are more contributing factors than mental state to why someone becomes powerful through chakra than just their mentality and pure physical training is one of them. He could've simply been really physically powerful which would be another factor complicating proving the chakra wheel hypothesis correct, because you can't say for sure whether the secret to ALL his power came from his mind, in addition to proving whether or not it specific values were a contributing factor against someone who got to similar levels of power but didn't share them. In the end there is too many factors to really prove which of these long dead shinobi was stronger, only that they were equal or near-equal enough that the differences were marginal and somehow, definitely stronger than everyone else. Which they probably got through a combination of luck and competency, like everyone else great.

Speaking of competency..."
Kimiko will continue practicing the Rasengan when they pass the Village Gate.