Tokyo - Japan bought 10% of €3.0bn in bonds issued on Monday by the eurozone's rescue fund, a government official said on Tuesday, less than its previous investments.
Japan's purchase came to €300m, the official at the finance ministry's international affairs bureau said.
Tokyo had bought 20% of previous bond sales issued by the European Financial Stability Facility (EFSF), the rescue fund.
"We took into account our euro liquidity (in Japan's special account of foreign currencies), terms on issuance and the market environment," the official said of the fall in the Japanese purchasing share.
Japanese leaders previously suggested Tokyo's purchase would stay around 20% but "it is not true that there is a fixed share" for Japan, the official added.
Japan has purchased a total of €2.975bn of EFSF bonds so far this year.