The oiled paper umbrella (kasayaki) festival is held to appease the souls of Soga brothers at their family temple Jozenji. The story of Juro and Goro is based on a real event in feudal Japan from 1193 when the brothers set their paper umbrellas on fire for torch at midnight to take revenge for their father’s murder.  

Juro was five years old and Goro three when they father Kawazu Sukeyasu was killed by Kudo Suketsune over a long disputed issue of feudal estate. Suketsune was a cousin of Sukeyasu and an important vassal of Shogun Yoritomo. The widow married a man named Soga who adopted the elder son Juro. The younger brother Goro was sent to a Buddhist temple to become a monk. But the two brothers had other plans than reciting holy sutras. They wanted to revenge their father.

The opportunity for avenging came when Shogun Yoritomo held a hunting session at the foot of Mt Fuji. At midnight, while a heavy storm was raging Juro and Goro found drunken Suketsune in the company of a prostitute and killed him. The elder brother Juro was killed and the younger Goro was captured. Shogun Yoritomo executed Goro but at the same time he honoured the brother's deed by reinstalling their mother as the legitimate owner of her late husband's estate. Goro was 20 and Juro 22 when they died.