The 'komahiki' event was one ritual that occurred within the imperial court in August each year when horses that were agisted in the Eastern provinces according to imperial edict were brought to the south hall of the imperial palace and paraded in front of the Emperor and afterwards nobility selected some whilst the remainder were stabled or allocated to the imperial guard.
Because the imperial agistment sites were required in four provinces (Shinano, Kai, Musashi and Kozuke), the plots of grazing land were dispersed and, according to ancient laws and political guidelines the ceremonies took place in an eight day timeframe in August.
Also, on the morning of the day prior to the ceremony another ceremony whereby a horse contributed by the officers and men of the imperial guard was taken to the Osaka no seki (the Osaka Barrier) in a ceremony called the Komamukae ('Horse Welcoming').
Later on, parts of the grazing land outside of Shinano Province stopped being used; however, to make up for some sort of shortfall etc the Oshu area had previously been acquired and it is also thought that influential local people contributed horses. The practice continued continuously up until around the time of the Onin War.
Besides this, on May 5 (lunar calender) each year preceding the 'komahiki' event, there was another ceremony where horses to be used in horseback archery and horse racing that had been presented to the emperor by princes and nobles were displayed in front of the Emperor.