Genshin Impact update 2.4 allows us to continue a series of quests that are related. To have access to this series of quests, it will be necessary to have unlocked the island of Watatsumi since it is on this island that we can start the quests of the priestess Tsuyuko.
How to unlock the Enkanomiya area?
First of all, it is important to have done the quest "The Still Water's Flow" to be able to unlock access to the Heart of Watatsumi. To activate the quest, you won't need to go see an NPC since it unlocks automatically by finishing the previous one. Your first step is to find Tsuyuko. She is next to Sangonomiya's teleport point.
Join Tsuyuko at the indicated location so that she can tell you about the Sigils and your next objective during a dialogue scene.
Then, you have to go to the two places indicated to collect the Sigils in order to unlock the altars.
To get the first, teleport to the nearest point at the top of Sangonomiya then head to the objective. Be careful, monsters are waiting for you so get ready to beat them.
As for the second, you have to go to the Heart of Watatsumi and to the place where you recovered the key to the moon-drenched depths during the previous quest. Again, you have to fight, but against Fatuis this time.
Now, in possession of the two Sigils, you will have to go to your two new objectives in order to unlock the altars. Rest assured, no fight is necessary for this step and you can just go for it.
Once done, return to Tsuyuko to witness a new dialogue phase. Just after, jump to go into the siphon created following the cutscene. The latter will teleport you to Enkanomiya. You now have access to this area, but take the opportunity to finish the quest by going to the teleportation point which is your last objective. To get there, go to the left.
