On top of upgrading your characters the Sango pearls are often used in Genshin Impact, while not that hard to find you'll still need a lot of them so here's a guide to where you can get your hands on a bunch.
Sango pearls Location Genshin Impact
You will be able to find Sango pearls on the Watatsumi island and Enkanomiya later on.
If you're looking for a more precise location for all these Sango pearls I'd advice checking the official interactive map where you'll be able to zoon as you see fit.
You can find the map on the Hoyolab website here.
