The government of Japan released The Status Report of Plutonium Management in Japan - 2021, which details its plutonium holdings. According to the report,
As of the end of 2021, the total amount of separated plutonium both managed within and outside of Japan was approximately 45.8 tons, approximately 9.3 tons of which was held domestically and the rest of approximately 36.5 tons was held abroad.
The amount of domestic storage, 9.3 tons, is slightly higher than that at the end of 2020, 8.9 tons. The difference is the 0.6 tons of plutonium in fresh MOX fuel transported from France in September-November 2021 and 0.2 tons of plutonium loaded into the Ikata Unit 3 reactor.
Of the plutonium stored abroad, 14,760 kg are stored in France (15,411 in 2020) and 21,780 kg - in the United Kingdom (21,805 in 2020). The reprocessing of Japan's spent fuel held in France had been completed by the end of 2017.
In 2020, Japan reported having a total of 46.1 tons of separated plutonium, of which 8.9 tons were held domestically.