You can't "create" stories with software. If you could, it would most likely turn out nauseatingly awful. Stories are the base of all good games, you must have some kind of clear story in-game for it to work. Now, as for coming up with them, listen to music, read other stories, gather inspiration so to say, then write down what you come up with.
Oh dark, the darkness that dozes in the dusk. Throw it all away. No one can break you, nobody can tear you. You live an endless life forever.
- Everett Bradley - Throw it All Away (Theme of Shadow)