The government of Japan released The Status Report of Plutonium Management in Japan - 2020, which details its plutonium holdings. According to the report,

As of the end of 2020, the total amount of separated plutonium both managed within and outside of Japan was approximately 46.1 tons, approximately 8.9 tons of which was held domestically and the rest of approximately 37.2 tons was held abroad.

The amount of domestic storage was approximately 8.9 tons at the end of 2020, the same amount as in the previous year, since there was no domestic consumption or recovery of separated plutonium either.

Of the plutonium stored abroad, 15,411 kg are stored in France (15,435 in 2019) and 21,805 kg - in the United Kingdom (21,180 in 2019). The reprocessing of Japan's spent fuel held in France had been completed by the end of 2017. The change of the amount of plutonium in the United Kingdom appears to reflect the change of the classification of the 0.6 tonnes of the material, rather than a new reprocessing campaign. In 2019 this material was reported as being contained in spent fuel. According to the report,

the stockpile held abroad increased from 36.6 tons to approximately 37.2 tons by adding approximately 0.6 tons of plutonium uncounted as of the end of 2019 among the plutonium separated under the contract with U.K.

In 2019, Japan reported having a total of 45.5 tons of separated plutonium, of which 8.9 tons were held domestically.