To advance Nari's storyline and gain her favor (and her "Keystone"), you typically need to navigate her "Pobie" obsession:
If you are stuck on a for Nari or Pobie, please let me know: What items do you currently have in your inventory? Which island are you currently on? What was the last thing Nari asked you to do? Leisure Suit Larry - Wet Dreams Dry Twice Pobie...
A key item needed for progress is a Joke Book , which you can find in a bush near the ruins outside. To advance Nari's storyline and gain her favor