When Zenkichi was 15 years old, he felt spiritual energy just before the day of the life-changing event of Zenkichi, he was happy and ran towards the border to share the happy event with his father but when he reached the border he saw his father was busy preparing the defense.
He understood the situation and gave an adjustable smile to himself as not to disturb his work, 'I will have more time to tell it after the beast wave,' he thought and walked back home in the warmth of the setting sun.
The lunar eclipse was a phenomenon when beasts lose their minds, though they still had little sense of wariness they couldn't control the urge to kill the people who go against nature. When humans started to evolve they started to give an aura that was against nature, so beasts could easily sense them.