Adopted by the Brotherhood of the Seventh Circle when he was only four years old Isao
developed a cold personality, having no attachment to anyone. He learned to do only what was
good for him even if it would harm someone else. That kind of attitude was aligned with the
Brotherhood's interests.

The Brotherhood is maintained by sabotage and assassination contracts.

Even with reasonable performance in combat and with Ninjutsu, Isao's physique is only
mediocre compared to the Brotherhood's Ninjas. During his training and on his firsts missions
Isao managed to stand out because of his strategic and tactical thinking. That was a kind of skill
that made him lonely since the other members couldn't keep pace with his process thought.

Normally the Brotherhood sends only one Ninja to each mission but when was the time to betray
the Shogun, twenty-five members were assigned to cooperate in an assassination mission. They
would work together to kill the supreme commander of Japan. Isao was the only one to be
against that plan, he argued that with so many Ninjas the mission would become a small war and
the Shogun would have options to flee during the confusion of the battle. Isao said that only he
and two other Ninjas would be enough to infiltrate the Shogun's residence and fulfill the mission.

Master Hi, the best strategist of the Brotherhood decided to support Isao's plan with a few
changes: six members would go on that mission with Hi himself leading them. The plan was
good, but for Master Hi, the young Isao was putting too much confidence in his skills and Hi
knew the samurai guarding the Shogun would fight to the death.

Master Hi divided the Ninjas into two groups. One for distraction purposes, to get the loyal
samurai away from the Shogun. This group would be lead by Isao having Master Hi's own
brother, Taru, as second in command. Taru was the newest master of the Brotherhood and the
best combatant of all of them. The second group, lead by Master Hi, had the goal of killing the
Shogun.

Master Hi's group failed. They injured the Shogun before all three Ninjas died by the
samurai swords, but the Shogun was still alive.

Isao and Taru were the only survivors and together they were able to kill all samurais and cut off the Shogun's head. Taru narrates those last moments with a mixture of gratitude and astonishment:

"In the end, only Isao and I survived. The Shogun was bleeding, but alive. We both knew that he
would take on revenge against the Brotherhood, so we decided to give our lives to fulfill that
mission. But I could never imagine that Isao would grow that much in that fight. In the
beginning, he was only supporting me while I would kill the samurais one by one. As the fight
evolved Isao was more and more aggressive and lethal.

It was as if each kill fed his desire to fight.

When an arrow pierced my left leg, making it impossible for me to fight at my best, we got
surrounded by twelve samurais. With the certainty of his victory, the Shogun reappeared to give
the order that would kill us both. Isao started to fight in a way I never saw. He was moving so
fast that for me was like the samurais couldn't see him. And he was so precisely lethal that with
each movement of his katana one samurai died even before hitting the ground.

In a matter of seconds, Isao killed twenty samurais and also the Shogun. He fulfilled the mission,
saved my life, and became something that even today I don't know how to describe.
Unfortunately, he doesn't remember those last moments of the fight and never again was able to
fight in that way."