The value was not available, but Dubai International Capital said in July it might buy stakes of up to $1.5 billion in one or two publicly listed companies in Japan.
A $1.5 billion investment would be equivalent of a 3 percent stake in Sony, which has a market value of 5.52 trillion yen ($50.9 billion).
This is Dubai International Capital's first investment in a Japanese company.
The announcement followed a newspaper report that the Chinese government's investment arm was likely to pick up shares in Tokyo, stoking hopes that foreign investors may be stepping up investments in Japan, which briefly boosted the yen.
"I personally have not heard overseas investors making positive comments on Japanese stocks in recent months and recent years," said Kazuya Nakamura, deputy general manager at Norinchukin Zenkyoren Asset Management.