The government of Japan released The Status Report of Plutonium Management in Japan - 2022, which details its plutonium holdings. According to the report,
As of the end of 2022, the total amount of separated plutonium both managed within and outside of Japan was approximately 45.1 tons, approximately 9.3 tons of which was held domestically and the rest of approximately 35.9 tons was held abroad.
The amount of domestic storage, 9.3 tons, hasn't changed since 2021. While about 0.6 tons were loaded into the Takahama Unit 4 reactor, approximately the same amount of plutonium fabricated into MOX fuel was transferred from France.
Of the plutonium stored abroad, 14,113 kg are stored in France (14,760 in 2021) and 21,757 kg - in the United Kingdom (21,780 in 2021). The reprocessing of Japan's spent fuel held in France had been completed by the end of 2017.
In 2021, Japan reported having a total of 45.8 tons of separated plutonium, of which 9.3 tons were held domestically.