The transaction forms of vegetables and fruits for processing are not spot market transactions but customer relationship contracts which are recognized as quasi integration. The terms of transactions are decided by not only competition but also negotiation between seller and buyer in the contracts. These facts can be analyzed only when we focus on the vertical site of market. This paper explains the vertical site by using Game Theory.

　The new facts are explained as follows. (1) Transactions with not the best but the second best are compelled because of opportunism. In order to weaken opportunism, save transaction cost, and to contract with the best, the customer relationship contracts are adopted. (2) The contract terms are decided by the relative bargaining power and the absolute bargaining power in the negotiation. The former is caused by the relationship with the second best. The latter is caused by the degree of the dependence on each other.

　By the case study of asparagus, sweetcorn, carrots and chinese leaves for processing, we can find some evidences for the theory. Farmers and processors adopt customer relationship contracts in order to defend nonfulfillment of spot contracts, that is opportunism. The price is raised in the area where the relative bargaining power of seller is strong. By the econometrics analysis, the empirical facts are explained as follows. The market structure is recognized as bilateral imperfect competition. The negotiated transaction forms are the mainstream. The formation of customer relationship contracts is premised on this situation. All kinds of negotiation are influenced by the bargaining power of both or either of farmers and processors. Transaction cost is saved in customer relationship contracts, but the extent of saving transaction cost depends on the transaction forms.

　This paper analyzes how the Korean farmers responded to the changes of agricultural conditions, and as the results, how the route of rice sale changed. The object of study is cooperative sale of unhulled rice, the general form of farmers-selling rice in colonial Korea.

　Until the 1920s, most farmers sold the unhulled rice to rice merchants in their own home. But with the fall of rice price, farmers had to minimize the loss. So the cooperative sale and farmers' sale of their product through regional shopping centers appeared newly. In the 1930s, the Government-General's policy of distribution-rationalization, the operation of examination in unhulled rice, and the construction of storehouse for agricultural product, increased cooperative sale.

　The form, the price, the quantity, and the stratums of cooperative sale can be summed up as follows. (1) The organizer of cooperative sale was the Aricultural Association of Korea. And the customers were rice exporters or rice-cleaning millers. (2) The price of cooperative sale was higher than the market price by ¥0.5-1.0. (3) Rice sold in cooperative sale amounted to 8,205,000 tons in 1939. (4) Total number of farmers who joined to cooperative sale was 650,000 in 1939. And small-scale farmers also joined to that.

　In the 1920s, rice sales were dominated entirely-by the route of farmer/unmodernized landlord-broker-rice merchant-rice exporter or rice-cleaning miller, and modernized landlord-rice exporter or rice-cleaning miller. But in the 1930s, new route of farmer/landlord-organization for agriculture-rice exporter or rice-cleaning miller appeared and spread.