TOKYO, Japan — Rakuten Inc. agreed to buy U.S. rebates website Ebates Inc. in Japan's largest e-commerce deal on record as the operator of the country's biggest online mall seeks overseas growth through acquisitions.Rakuten, controlled by billionaire Hiroshi Mikitani, will pay about $1 billion for all of Ebates, it said in a regulatory filing today. San Francisco-based Ebates offers cash rebates to customers who buy products ranging from laptops to lipsticks from the website’s retail partners.The deal comes after Rakuten has announced 18 acquisitions announced since the start of last year, and the cybermall operator said in June it’s open to more large-scale buys following its bond debut. Rakuten bought messaging service Viber Media Inc. for $905 million in March, Japan’s biggest e-commerce deal at the time according to data compiled by Bloomberg.As of June 30, Rakuten had about 1.7 trillion yen ($16 billion) in cash and short-term investments, according to data compiled by Bloomberg.Rakuten fell 1.3 percent to 1,254 yen at the close of trading in Tokyo, the lowest level since May 23. The stock has lost 20 percent this year, compared with the 0.2 percent decline in the benchmark Topix. The shares dropped the most in three months on Sept. 8 on concerns about the deal’s cost effectiveness, after Rakuten confirmed it was in negotiations.By Yuki Yamaguchi; editors: Stephanie Wong, Daryl Loo, Subramaniam Sharma.