It recently launched an instant messaging app for personal computers that allows users to make outgoing mobile calls to other Viber users and to non-registered mobiles, making it a rival to Skype.
Rakuten has been on an overseas buying spree in recent years as it seeks to expand outside its home market Japan, where economic growth remains sluggish.
Rakuten has acquired e-commerce providers from Brazil to Germany, as well as Toronto-based eReader business Kobo and online video providers Wuaki.tv of Spain and Viki of Singapore. In 2012, it made a large investment in website Pinterest.
(Read more: Messaging apps hit gold as 'emojis' head west)
In the 12 months ended Dec. 31, Rakuten's operating profit jumped 80 percent to 90.2 billion yen ($882.89 million), marking a sixth consecutive year of record earnings, though lagging the average 99.9 billion yen projected by 18 analysts polled by Thomson Reuters Starmine.
Net profit doubled to 43.5 billion yen, while revenue rose 30 percent to 518.6 billion yen.