Japanese e-commerce firm Rakuten is branching out.

Following an announcement of a new partnership with Walmart to launch an online grocery delivery service, the company announced this week it had received approval from the Japanese government to enter the mobile network operator business.

Speaking to CNBC's Akiko Fujita on Wednesday, Rakuten CEO Hiroshi Mikitani said the mobile business is a "very, very important" platform for services from e-commerce to content.

That's why there's a trend of mergers between content and networks in deals such as Verizon buying Yahoo, Mikitani said.

"In the future, we're going to see the conversion of network platforms and content and transactions."