Seirai Island is sprawling with treasures, and The Relics of Seirai brings the Traveler and Paimon together with another treasure-hunting personality who's determined to uncover the spoils left behind by her ancestors.
The World Quest doesn't automatically fill your Quest menu. Unlock it by heading over to Koseki Village (the exact location is marked up in the image below), where you'll encounter a certain Fujiwara Toshiko who's found herself in a pickle. She's surrounded by Hilichurls—defeat them and interact with her to initiate the quest.
Fujiwara Toshiko is sure about the treasure's location and asks for your protection until it's found. After promising to share part of the reward, you agree to help. She gives you the Fujiwara Toshiko's Treasure Map, which displays a peculiar code on the bottom right.
You can find the map in the Quest Item section of your Inventory. The code contains three symbols, and the arrows indicate the order in which you should trigger them (clockwise). Continuing the quest, you'll find that there's a mechanism beside Fujiwara Toshiko. Activate it to begin the first puzzle.
First Puzzle
Simply step on the symbols circled above in the same order as the code on the map. That's the right side first, the left second, and the middle last. Doing so will open up the basement, which you should venture into to continue the quest.
As a bonus, you'll find an Electroculus and a few Investigation points inside the basement—one of which contains an Enigmatic Page. So don't forget to interact with them!
Second Puzzle
Speak with Fujiwara Toshiko, who's standing right beside another mechanism. After, activate the mechanism to start the second Light-Up Tile Puzzle. Follow the route above to guide your steps, which should start on the tile marked with a circle at the bottom-right (with the locked Chest as the northern point). This route also follows the same order of symbols in the Treasure Map.
Third Puzzle
Speak with Fujiwara Toshiko once again before activating the same mechanism to begin the third puzzle. This time, start from the bottom-left and make your way upward in a zig-zag. Remember to follow the exact route marked above, which will light the tiles up in the same order as the symbols on the Treasure Map. Otherwise, the puzzle won't complete!
After the third puzzle, the Chest will unlock and Fujiwara Toshiko will check the spoils, only to find a single picture of seemingly no value. Disappointedly, leave the basement and accompany her back to camp—the exact location is highlighted by the quest marker on the map.
Along the way, you'll encounter Treasure Hoarders, a Masterless Samurai and his cronies, and Fatui Skirmishers, all of whom are interested in the treasure. Defeat them and make it to the camp to complete the quest.
Completing this World Quest will unlock the Achievement It Has to Be Treasure.
Love treasure? Check out our guide on All Nameless Treasure Locations in Genshin Impact.