Japan's main governing party has started interviewing four information technology giants before drawing up proposals to ensure fair competition in the sector.
A Liberal Democratic Party panel held a hearing for officials from Apple and Amazon on Friday.
The two firms, along with Google and Facebook, are collectively known as GAFA. They face criticism for collecting huge amounts of customer data and using them to remain dominant in the digital market.
Japan's government is considering setting rules to ensure a fair market environment.
Apple and Amazon agreed to take part in the hearing on condition that what they told lawmakers would not be disclosed.
Participants say the two companies told lawmakers that their dealings are fair and transparent.
Some panel members reportedly pointed out that Apple lacks transparency in how it screens apps developed by other companies and sold on its platform.
The members also asked whether Amazon keeps data only for itself and blocks entry by new companies.
The panel plans to interview Google and Facebook next week and submit proposals to the government in April.
Amazon Japan official Hiroyoshi Watanabe told reporters that the lawmakers asked many questions and that he answered them sincerely.
Watanabe said he told the panel that his company is willing to continue dialogue.