Chongryon -- the General Association of Korean Residents in Japan -- is being leased the building by its new owners, reports said, apparently ending months of uncertainty after Japanese courts ruled it had to sell.
A Japanese real estate company took over ownership of the 2,390-square-metre (25,725-square-feet) plot and 10-storey building in November, after a forced auction to repay outstanding debts.
Marunaka Holdings, which paid 2.21 billion yen (USD 18 million) for the site, told AFP today that the company had subsequently resold the property to real estate firm Gurin Forisuto.
Under the laws governing forced auctions, the party selling cannot take part in the purchase.
However, no such restrictions apply to a subsequent resale, and media suggested there was some evidence a company that may be affiliated to Chongryon was involved in the secondary transaction.
No one from Gurin Forisuto was immediately reachable for comment, while a spokesman for Chongryon told AFP: "we are not aware of the reports and at this point we don't know about" the fate of the de facto embassy.
Hundreds of thousands of ethnic Koreans live in Japan, mostly a legacy of those who emigrated or were forced to move to Japan during its 1910-1945 colonial rule of the Korean peninsula.
About 10 per cent are believed to be affiliated with Chongryon, which charges that the community is persecuted by authorities and harassed by right-wing activists.