koobas.hobune.stream
I want to create app in mobile and PC. what should I use for the database?
I want create backend (admin) in PC and other users on mobile.
XML, JSON would probably be the best bet for a general use case that's also easy to transfer to game data. If your game is going to require a connection then you'd send data to clients from the server and only hold it there if you're worried about the human readability of XML and JSON.
If this is the route you choose to go, then I would personally also use a database like mySQL or another DBMS software to actually store and maintain the player files.
