In Japan, under the Tokugawa shogunate, 1603–1868, registered peasants were guaranteed their property right of their farmland, but regulations on farmland trades restricted their access to financial markets and they were allowed to pay land tax in kind, which meant peasants were shielded against risk from volatility of financial market, land market and commodity market. Under the regulatory shield, millions of peasant family continued to be owner farmers and wealth inequality was kept small. However, during the Meiji Restoration from 1868, the government redefined peasants’ claim as the full-fledged modern property right, fully deregulated the land and financial market, and obliged landowners to pay land tax by money. With owner-peasants directly exposed to market risks, the ratio of tenanted land increased from 30 percent in the 1870s to the 50 percent in the 1900s. Behind the drastic redistribution of landownership, there was a new role of landlords replacing regulations: shielding tenant farmers against market risk. This institutional feature of tenancy contract was originally discussed by a Marxian economist Moritaro Yamada in the 1930s, when the mechanism had begun to collapse in the Great Depression. We attempt to formulate risk sharing mechanism managed by landlords, motivated by Yamada’s work.