(Updates with closing share price in fourth paragraph.)

Feb. 28 (Bloomberg) -- Rakuten Inc. President Hiroshi Mikitani and his wife Haruko, who own 43 percent of Japan’s biggest online retailer, plan to sell 36 million shares worth $328 million at yesterday’s price.

Sumitomo Mitsui Trust Bank Ltd. was hired to make the transaction, according to a filing with Japan’s Finance Ministry yesterday. The contract with the bank runs from Feb. 21 to Dec. 27, according to the filing, which didn’t say why the shares would be sold. A company spokeswoman declined to comment on the filing.

Rakuten had surged 24 percent in 2013 before today, the fourth best performer on the 60-member MSCI World Retail Index during the period, giving it a market value of 1.1 trillion yen ($12 billion). Mikitani is the largest stockholder with a 32.5 percent stake. He holds the shares directly and through his Tokyo-based consulting company Crimson Group. Haruko Mikitani owns about 11 percent, according to data compiled by Bloomberg.

The online retailer and Internet mall operator dropped 4.1 percent to 801 yen, the lowest in a month, as of the close in Tokyo trading today.

Mikitani is Japan’s third-richest individual with a net worth of $5.3 billion, according to the Bloomberg Billionaires Index. The 36 million shares the couple intend to sell would be worth about 30 billion yen at yesterday’s closing price.

Japan’s benchmark Nikkei 225 Stock Average has gained 10 percent this year, partly because a depreciating yen has boosted the value of exporters’ overseas earnings.

--With assistance from Patrick Chu and Naoko Fujimura in Tokyo. Editors: Dave McCombs, Frank Longid