This research aims to reveal the direction of Japan's rice farming industry under the TPP regime based on field surveys of rice farming industry in California and by examining California's economic efficiency and environmental friendliness. The final goal is to devise solutions to policy makers and people in rice industry in order to enable the co-exist of rice farming industries of Japan and the US under the TPP regime, and to achieve sustainable growth and development in the Trans-Pacific region. This research has a Contemporary Focus because it investigates how Japan-US economic relations should be established in the context of the TPP regime, especially with regard to agriculture. It is also strongly concerned with Policy Relevance in order to help find solutions about rice issues, which has been the most controversial issue in Japan-US trade negotiations. Further, this project adopts a Comparative or Transnational Perspectives, by focusing on the search for common interests that Japan and the US could potentially share, after identifying differences between their rice farming industries. Very few recent studies show the realistic prospects of Japan's rice farming industry from a comparative perspective. This project, which is based on field surveys can reflect the newest trends and prepare realistic solutions for policy makers and people in rice industry, having recognized that Japan would be at a disadvantage to California, which is a direct competitor to Japan's rice farming industry under the TPP regime. In this research, I examine the following: (i) technical and social conditions of winter flooded fields that represent an achievement of both economic efficiency and environmental friendliness in California; and (ii) investigating the possibilities of expanding rice exports to Japan. By conducting these two tasks, first, I can reveal the economic and environmental advantages of California's rice farming industry compared to Japan's, analyzing components of technologies and social relationships. I can compare Japan with the US in terms of the different farmland conditions and farming systems that help to enhance efficiency, the concept of institutions that is necessary for improving environmental friendliness, and the approaches that society can employ. These findings will help determine to what extent Japan's rice farming industry might catch up with California's, and I can also figure out the level to which Japan's rice farming might reduce its costs, while improving its environmental friendliness. I can then estimate to what degree Japanese rice would be substituted by that of California in Japan's market due to its low production cost. On the other hand, to maintain the present amount of production, we can show that Japan's rice farming industry would be forced to increase exports to overseas markets based on improving high-added value or to change from producing staple rice to multi-purpose rice including feed rice.