When I think of Final Fantasy XV two of the things that jump to mind are a sprawling, detailed, lengthy RPG, and the gorgeous and highly-detailed look of the game. The PC port of the game is 170 GB for a reason: it's a sprawling adventure that in no way lends itself to being squashed down in size, nevermind onto some weedy device like a mobile phone. Wait I'm being handed a piece of paper here and... oh. That's exactly what Square Enix is doing.
Final Fantasy XV Pocket Edition is the full story of the console game, retold with cute chibi characters, simplified touch screen gameplay and split into episodic chunks. It's a way for people with minimal time available to experience the story, with gameplay tailored to playing on your commute.
While no release date was given beyond Fall 2017, the game is coming to iOS, Android and Windows Phone, with the first of ten episodes available for free, and the remainder available to purchase from day one.
If you feel like revisiting EOS but don't have countless hours available, this might be a cute option to look at.