I've talked this to death already. It's practically fact at this point too. But thanks to a better Japan researcher it looks like there's even more to the story. Man MiHoYo went deep. 
Side Note: Also just want to say Gaijin states that his last video on the subject did poorly. The game he's talking about I don't even know if any players on this side of the world really know. But you know what we do know? Genshin. The guy really needs to get over his gacha hang ups. Imagine if he brought up the subject with relation to this game? Well hopefully his fans will help him figure that out.
Anyway a long while ago I talked about the many different inspirations Yae's character took from Japanese folklore. One of those things is shown through her weapon the Kagura's Verity. Kagura is the name of a dance that a higher Shinto goddess Ame no Uzume performed to get the Sun Goddess Amaterasu to finally leave her room which is reflected in Genshin by Yae manipulating the events of the Archon Quest to get Ei to finally leave her room the Plane of Euthymia.
Well thanks to Gaijin expanding on his last video we now know that even in the iteration of the story that he talked about Ame no Uzume still took center stage. Last time he said it was a mirror that Amaterasu saw her reflection and realized her importance to Japan that got her to leave her room. In this video he explains that that mirror is Uzume's mirror which ties even more directly to Yae's Voiceline about Euthymia.
And that mirror alongside the maga***a both belong to Uzume and have since become 2 of the 3 regalia of Japan the third being SusanoO's sword. That ties Yae and not Ei directly to royalty which makes sense knowing that their dynamic was the Tenno usurped by the Shogun which started the Shogunate period.
Then there's that second story which I had no idea about at all. But I did talk about the part I did know a long time ago. When I was talking about Istaroth's Inazuman name Tokoyo I brought up an Okinawan myth.
As the story goes a girl named Tokoyo descended into the sea and fought a dragon under the command of Okuninushi. She discovers the dragons were cursing the Tenno because a statue of him had sank into their realm. By bringing the statue back up out of the water Tokoyo saved the Tenno. Now in other Japanese mythology Okuninushi is an earth kami and original ruler of Japan who would eventually abdicate in favor of human rule. Okuninushi would then take up rulership of Tokoyo no Kuni the Japanese underworld. (also a name for Enkanomiya but there's different reasons for that)
Now in Gaijin's version he names the leader of the earth kami Sarutahiko no Mikoto. From what I can find it's up for interpretation. Both of these guys are equals in strength and status in Japanese folklore. Either way the story goes that Ame no Uzume is the one that finally convinces the kami to allow humans to rule over Japan. This plays into the Human Age which is a major point in Genshin and what the original Seven are guiding humans to do. We saw this succeed in Liyue with Zhongli cultivating the Qixing to take over. We actually see Yae doing this too during the Irodori Festival. She's the one that inspired Ayato and the entire plot of the event. On top of that she met with Kokomi too to discuss the relations between the two nations.
On another note Tokoyo saving the Tenno plays out in a way too. In my theory on how things happened in Inazuma Yae worked with Istaroth to set the Sacred Sakura plan in motion. How does she even know the shade though? What if Istaroth not only helped Yae during that plan but also was the reason she managed to survive as a spirit to begin with? Similar to how Tokoyo brought the statue of the Tenno out of the water (the underworld is usually depicted as being underwater) what if after Ei killed the original Archon it was Istaroth that reawoke her and led her to kitsunetsuki'ing Yae?
Anyway it's really cool how much there was still left to discover about this topic. 
Tips and Tricks from a Super Casual Genshin f2p
