Epic Games Inc.’s decision to sue Apple Inc. over its mobile store practices has sparked new scrutiny in the massive Japanese gaming market, prompting complaints and questions about how to counter the tech giant’s dominance.

While Epic, publisher of the hit title Fortnite, focuses on the 30 percent revenue cut app stores typically take, Japanese game studios have broader concerns. They have long been unhappy with what they see as Apple’s inconsistent enforcement of its own App Store guidelines, unpredictable content decisions and lapses in communication, according to more than a dozen people involved in the matter.

The nation's antitrust regulator said it will step up scrutiny of the iPhone-maker’s practices in the wake of the high-stakes legal clash. And in rare cases, prominent executives are beginning to speak out after staying silent out of fear of reprisal.