You cannot access Tsurumu Island without accepting the A Particularly Particular Author quest from the guild. This World Quest is unlocked after you have completed Seirai Stormchases World Quest
Tsurumi Island is covered in a thick mist, and if you wander too far in, you'll get a message saying, "You lose your way amidst the mist and are returned to where you started."
How to not get lost in the Mist
To explore Tsurumi Island in peace, you need to find and locate Stormstones. These are ritual stone piles that have been left from the civilization previously on this island. To activate these Stormstones, you need to imbue them with Electro—hit them with an Electro attack. When activated in a specific radius, they will prevent you from getting lost.
But some of these ritual stones already have a white light in. If the white light is there, then the Stormstone is active, and you can travel into the fog without issue.
If the light is not there, hit it with an Electro attack, and then as you explore, keep lighting them up with Electro so you do not get lost in the mist. The second, you see the outer edges of the screen become fog-like. You've gone too far and need to backtrack a bit.
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