The hidden passageway, underwater teleporter, and domain
Follow the passageway until you reach a massive cavern with a shipwreck.
Further ahead, you’ll see the teleport waypoint that you can tag so that it remains activated. There’s also a chest here, but you need to defeat another tough samurai.
If you inspect the crates in the shipwreck, you’ll get another Old Stone Slate for the Amenoma Kageuchi.
Continue to the opposite side of the passageway to find a familiar area. You’re actually just above the Perpetual Mechanical Array’s arena. If you go a bit to your right, you’ll find a Thunder Sakura Bough that can spawn an Electrograna.
You can use this to grapple (“T”) to reach a small nook. This has an Electroculi for you to collect.
Back at the main area overlooking the Perpetual Mechanical Array, you’ll spot a switch. Activate it to start a floor puzzle.
The goal here is to walk around to step on the plates, making all of them glow, until you reach the last plate with a beam of light. You can’t step on the same plate twice, and you can’t jump/glide to cross a gap.
Successfully completing the puzzle lets you open the gate. Inside this room is an Earth Kitsune and another floor puzzle. For this one, simply loop around and touch the edges.
Then, walk on the central plates until you can step on the one with the beam.
This will spawn a treasure chest. Moreover, it’ll also reveal the “Empty Boats of a Thousand Gates,” the underwater domain that we’ve been searching for.
That’s it, you’ve discovered the secrets here and, even better, you’ve got two fast travel points that are closer to the Perpetual Mechanical Array. Likewise, you’ve finished the Araumi Sacred Sakura Cleansing Ritual. Don’t forget that there are still a couple more locations that you can visit in Genshin Impact‘s Inazuma region. These are found in Chinju Forest and Kamisato Estate. Then, after you’ve completed these, it’s time for the finale.