I like "story" more coz it flows smoothly. But if you decide to use "fable" it is fine too coz it is the one they used in the novel. The "narrative" stuff is used in ranking the stories and the constellations in the novel so i don't think it's fitting to use that coz it has it's own use already.
This is just an example so...
Just imagine when they say this:
[the narrative grade, narrative 'pebble and i' is...] <<<this sounds so cringy.
[the narrative grade, story 'pebble and i' is...] <<<sounds fine.