

The Oniwaban was an elite of ninja who were at guard of the Edo Castle
during the Togukawa Era.
For hundreds of years the IGA (Togakure) group of ninja were the major
force in Ninjitsu, however smaller groups existed in other parts of Japan.
Within these groups of spies, saboteurs, and killers, another family incread
its power, namely the deadly KOGA of Shiga prefecture.
Interestingly, Shiga is next to the Mie prefecture in southern Japan.
So, the KOGA and IGA inhabited the same mountain range, in two valleys
divided by a mountain.
During the centuries, several leaders such as Takeda Shingen, Oda Nobunga,
and perhaps th
e
greatest general in Japanese History, Tokugawa Ieyasu all employed the
Ninja to help control the country through a complex spy network.
With the close of the Sengoku era in 1600, three hundred years of peace
and prosperity followed, known as the Tokugawa era. Up until this time
the capital of Japan had been in Kyoto, but Tokugawa moved the capital
to Edo (Tokyo today). He took with him three hundred Ninja from the KOGA
and IGA groups as personal bodyguards. So the 'Oniwaban' group of ninja
set, not as an espionage unit, but as an internal security unit. Later
these Ninja guarded the castle in Tokyo.
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These are all the information I've been able to find. If you notice any
error or have more information, please contact me by e-mail.^_^