If you're willing to settle for interactive fiction, Borogrove is reported to work well enough on a phone, and for an offline app there's Fabularium. Sadly Twine isn't really usable even on tablets, if I remember correctly.
Edit: for a mobile app to export APKs is a tricky proposition. Google intentionally makes it hard through licensing and technical means. But I think Termux might include a way to do that. I haven't actually tried.