In Japan, the government has set a target for a reduction in greenhouse gas (GHG) emissions by 26% from 2013 levels by 2030. The commercial sector has the highest reduction target—39.8%—among all Japanese sectors. This chapter first presents the current GHG situation in Japan and Japanese climate policy in the commercial sector. Second, we introduce a nationwide survey that we conducted on the implementation of energy efficiency measures (EEMs) in office buildings with large-scale emissions in Japan. The survey results show that energy-saving technology adoption is more advanced in Tokyo than in other prefectures and that there is more space for the adoption of energy-efficient technologies nationwide. To accelerate EEM adoption to achieve the 2030 target, regulatory agencies must improve the way they promote energy audits and subsidies and provide information on energy savings.