In January, the East Asian country purchased 864,000 kiloliters, equal to 192,000 bpd, Japan's Economy, Trade and Industry Ministry announced in its latest report on oil imports.
Japan had imported 641,000 kiloliters, equal to 143,000 bpd in December 2014, according to the report.
Iran is the 5th country in terms of supplying Japan’s demand for oil in January 2015, the ministry said.
Asian imports of Iranian crude oil increased by 19.8 percent last year to hit a three-year high, despite Western sanctions against the Iranian oil industry over the country’s peaceful nuclear program.
Imports by Iran's four biggest buyers - China, India, Japan and South Korea - averaged 1.12 million barrels per day (bpd) in 2014, government and tanker-tracking data showed, the highest since the region took more than 1.5 million bpd in 2011.