Back then, the Jinchuriki had been unable to perfectly control the Eight-Tails' power.
Elite ninja such as the Third Raikage would step in to stop it whenever the Eight-Tails lost control.
Although Kumogakure could always stop the Eight-Tails' rampage and seal it inside the Sealing Jar.
But every time, many people would be killed or injured.
Still, despite the risks.
To maintain an advantageous position in the balance of power with other countries, they had to control the Eight-Tails' power.
So they continued their Jinchuriki experiments.
Motoi: "One of the deceased... was my father!"
Everyone: "!"
Yamato frowned. He had not expected there to be such a past. "Your father was killed by Mr. Killer B... so..."
"No."
Motoi shook his head.
"Mr. Killer B and I were friends. When my father died, we were only two five-year-old children... The Jinchuriki who killed my father..."
It was Blue B.
In other words, the Fourth Raikage's cousin.
"When the Eight-Tails was extracted from him... he died... Not long afterward, Mr. Killer B became the Eight-Tails' next Jinchuriki..."
Yamato was puzzled. "Then why... did you want to kill Mr. Killer B?"
"Controlling the Eight-Tails was impossible. I believed that many more people would continue to sacrifice themselves... On top of that, after my father's death, my mother cried all day long, and our family gradually fell apart. So I began to hate the Eight-Tails more and more... Although I was only a child at the time, I kept trying to find a way to take revenge..."
Motoi shook his head.
"Mr. Killer B was always smiling. As I gradually sank into a whirlpool of hatred, I transferred that hatred to Mr. Killer B, who knew nothing and kept smiling. In other words... my hatred for the Eight-Tails ultimately shifted onto Mr. Killer