Japanese history includes the conquests by the Yamato Imperial Court, which held influence over the Kinki region. However, history is written by the victorious, and future generations can only read what is recorded.
In the 9th century, Japan was divided into three regions: western Japan (Kyushu), which was under the control of the Yamato Imperial Court (Kyoto and Nara); the Kanto region (around Tokyo), which followed the court reluctantly; and the Tohoku region, which did not follow the court at all.
Taira no Masakado was a powerful family from the Kanto region, originally descended from a noble family that had been defeated in a power struggle within the court and had migrated to the Kanto region to settle down. He was the fifth generation of Emperor Kanmu.
The inhabitants of the Kanto region suffered from heavy taxes imposed to support the extravagance of the imperial court. In 935, Taira no Masakado drove away the officials sent by the court, declared himself Emperor of the Kanto region, and attempted to establish an independent country. Although the rebellion was eventually quashed and he was declared a renegade, there is a sense of admiration for him among people in eastern Japan. The Umaoi Festival in Soma pays tribute to Taira no Masakado.