Someone told me about a ~2009 Naruto fanfic from Fanfiction.net that featured some likely American girl.
The girl, who from birth or so, secretly used a power of 'XP counter and allocation' to be better at things, with one mentioned method of using "manga trivia" as an easy source of experience to shift into some other skill?
And using that experience literally caused her to lose her memories of it.
But, she's not the POV character. Instead, XP girl is the cause of the POV character, her sister, entering the Naruto world, by dragging her in.
Does anyone know this story?