In 991, Emperor Ichijo ordered to build Upper shrine on the top of Mt. Hachiman and lower shrine on the bottom of of Mt. Hachiman. It was well respected by imperial families and all other Daimyo.
After the battle of Sekigahara, Tokugawa Ieyasu worshiped this shrine for long-life-peace and gave land to this shrine. 3rd Tokugawa Shogun, Iemitsu and Ietsuna also worshiped this shrine.
After Hachiman Castle was abandoned, Hachiman Shrine became the guardian of Omi-Hachiman and Omi-merchants.
Two Himatsuri (Fire Festival)
... was originally started by Oda Nobunaga when he was in Azuchi. In new year's day, he dressed up with unique costume and paraded from Azuchi Castle to all town. When Hidetsugu moved Azuchi town to Omi-Hachiman, it became the festival for Hachiman Shrine. Now, it's a fire festival with Dashi, parade floats. It is held in every March.
... is started in the time of Ojin. When emperor Ojin traveled Omi, all town made a pass of torches for him. This was the origin of the festival. This festival has the same history of this shrine, so it has been continued for over 1,800 years. It is held in every April.