The origin dates back to the "Nine Years' War" in the Heian period. When Minamoto no Yoshiie and his father, Yorinobu, set out to subdue the Ou region, they prayed for victory at the Okunitama Shrine. As an offering in gratitude, one of the sacred foods was a plum. Since ancient times, plums have been considered fruit that wards off evil spirits. Because of this, a plum market came to be held in the shrine precincts, giving the festival its name. Even today, shops selling plums line the approach to the shrine, bustling with many people. Additionally, "karasu fans" (karasu uchiwa) and "karasu folding fans" (karasu sensu), which are believed to provide blessings for a good harvest, protection from epidemics, and warding off evil, are also distributed.