On top of upgrading your characters the Fluorescent Fungus 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.
Fluorescent Fungus Location Genshin Impact
The only place you'll be able to get the Fluorescent Fungus is the misty Tsurumi Island.
If you're looking for a more precise location for all these Onikabuto 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.
