Shomu refers to the actual practice of control and administration over kanno (encouragement of agriculture), trials, and the collection of taxes within shoen (the manor); it also refers to the individuals who were authorized to practice shomu. The authority in regard to shomu is referred to as shomuken (the authority of the jurisdiction and the administration of shoen).
Shomu was originally derived from the authority held by kokuji (provincial governors) who exercised it to administer the matters regarding the ryoseikoku (province). Shoen was often placed under the complicated control system due to repeated donations; the honjo (proprietor or guarantor of a private estate) originally referred to the individuals who held the shomuken, and those who were in the position to hold the shomuken could administer various authorities against the local power within shoen, such as shokan (an officer governing shoen) and shomin (people of the manor), by personally going to the shoen himself or by sending a zassho (a person in charge of miscellaneous tasks) there. As such, there were often quarrels as to who holds the shomuken.
However, since the Kamakura bakufu (Japanese feudal government headed by a shogun) had established the jito (estate stewards), who held the right to judge criminal cases, the authority of the shomuken and honjo themselves eroded; and further, as the cases of 'Ukeoi shoen, ' which was the contract system in which the shoen owners entrusted the shomu to Shugo and Jito (military governor and estate steward) or to the locally influential individuals in return for the exemption of the payment of the certain amount of nengu (land tax), increased during the period of the Northern and Southern Courts (Japan), the shomuken virtually lost its substance.