Soul Emperor From Other Land Chapter 59

"I've said before that during the Warring States Period, the Senju and Uchiha clans were the two most powerful ninja clans."

"Especially after Hashirama Senju and Madara Uchiha inherited the position of clan leader, the strength of the two families is completely not on the same level as other families."

"And the strength of the two families is not only the strength of the two clan leaders, but also that every ninja is first-class strong in the same level."

"It is precisely because of the strength of the two families that an employer chooses the Senju. Another employer with the opposite interest will inevitably choose the Uchiha, and vice versa."

"So the hatred between the two major ninja clans is also the deepest."