The term "Zoyakumen" (or Zoekiden) means myoden (rice fields named after the local land lords who developed the land in question) which were exempted from zatsueki (levies other than land tax) under the system of shoen (manor) and kokugaryo (territories governed by provincial government) during the medieval period.
Zoyakumen are categorized into several types. The first type was land certified by kokushi (Provincial Governor) as Zoyakumen kei shoen (shoen originated from Zoyakumen) and whose lords paid kanmotsu (tribute goods paid as tax) to kokuga (provincial government offices) while securing kuji (public duties)/zatsueki (odd job tasks) for themselves. The second type was land called beppu/betsumyo, developed by local officials/gunji (local magistrate) and certified by kokushi as Zoyakumen. Although this type of land was basically yusoden (rice fields subject to taxation), they were certified as Zoyakumen. Against the background of the established fact of Zoyakumen, these lands later obtained fuyu no ken (the right of tax exemption)/funyu no ken (the right to keep tax agents from entering the property) as kishinchi kei shorn (shoen originated from donated lands) or became the unit of kokugaryo, which was then consisted of many shoen. During the Kamakura period, some landlords of Zoyakumen became jito (manager and lord of shoen), and they imposed zatsukuji, which corresponded to kuji other than buyaku (compulsory labor service), and zaikeeki, which corresponded to zatsueki, for their own interest while calling farmers zaike. The last type was land called sanden (deteriorated rice fields), not qualified for myoden because farmers lacked the ability to bear zatsueki due to poor harvests.