After the withdrawal of the United States from the Trans-Pacific Partnership (TPP) in 2017, Japan has taken the lead in advancing the TPP framework via the CPTPP to reform its highly regulated sectors such as agriculture and medical services. This chapter analyzes Japan’s participation in the TPP regime by (1) examining the expected impact of changes in rules and regulations that have come to be institutionalized as “entrenched regulations” or ganban in those sectors; and (2) simulating the macroeconomic impact of TPP membership on Japan and other TPP member countries, using a GTAP database and a CGE model to analyze global trade outcomes. The simulation scenarios show the framework of TPP12 and model the economic impact of and third party country spillover from the reduction of non-tariff measures (NTMs).