What or how are adult sites distributing successfully? I think the biggest paid sites have apps. But I’ve never personally heard of any one using any porn tube site app or anything. Browsers are used.
In Japan, DMM is a very diversified company (it runs a very well known hackerspace, for example), and a very profitable business comes from mobile-oriented games. Many of the erotic mobile-oriented games have a web browser version or PC version, and the more recent ones have native apps as well. In addition some have a censored version as well sharing the same account.
The app store is just called DMM Games store [0], since it distributes both its age-unrestricted games as well as games under its adult imprint (Fanza) via it.
With videos, since stores of videos are allowed on the play store, you instead have the situation that the DMM videos app is available on Android and iPhone, and the Fanza imprint is separately downloadable on Android [1, nsfw, needs vpn]
I’m genuinely curious. I have no clue.