Acquisition Type: Quest
For the Island Token you need to complete the quest My Truest Friend. To start it you have to interact with the object near the entrance of the island. After that you have to interact with phantoms/objects or wait in orange circles. You can see the exact path on the picture below. After that you have to enter the dungeon and interact with 4 objects. These can be seen in the pictures below the path.
Objects to interact with
Mokoko Seeds and other locations
Click me to show the island again
Right-click on the map to open worldmap