The Ghost of Tsushima fox dens and Inari shrines are side quests and collectibles players can find, and depending on how many of their locations you can work out, you can massively increase the number of charms you can equip at once and even upgrade the ones you have.
When you find a fox den, marked by tall, colorful trees of either red or yellow, the trick is to find the living fox in the area, and then follow it. Follow it for long enough and it'll lead you to the Inari Shrine, which you can honor to get the charm upgrade and complete the area.
