After you find a fox den, follow the fox. It'll take you to an Inari shrine. Honor the shrine to complete the fox den. Praying at Inari shrines opens up more charm slots. Once all slots are unlocked, praying at the shrines increases charm power. There are 49 Inari shrines in total.
Some of Tsushima's shrines are dedicated to Inari, kami of agriculture and plenty. Foxes are Inari's messengers, and are often drawn to these sacred places.
Find and honor the island's shrines to Inari.
