EiMikoSara

EiMikoSara is the poly ship between Kujou Sara, Raiden Ei and Yae Miko from the Genshin Impact fandom.

Canon
Ei, Miko, and Sara each have a voice line about each other. Along with that, they have all interacted at least once separately. Their color schemes are also very similar, as Ei and Sara have purple hair, and Miko has pink hair, which is very similar to Purple. Each have a different relationship with each other. Yae and Sara are practically enemies, Ei is Sara's ruler (Sara also being her loyal-general), and lastly, Yae and Ei get along very well.

The three have a couple of similarities. They're all from Inazuma, all have an electro vision, and have similar personalities.

Fanon
A common reason why the shippers are drawn to this trio is because of the parallels between Yae Miko and Kitsune Saiguu, and Kujou Sara and Sasayuri. Kitsune Saiguu and Sasayuri are both deceased close friend of Raiden Ei, and they're a kitsune and a tengu warrior respectively. Because of their similarities, sometimes fans consider Miko and Sara as reincarnations of Ei's late friends.

Another fascinating aspect of their relationship is their difference in status: Raiden Ei sits at the top as the Electro Archon, Yae Miko is her second in command and her familiar, and Kujou Sara is extremely faithful to Inazuma and its Archon. Though this creates a power imbalance between Sara and the other two, it's not uncommon for the fans to explore and subvert the power dynamic, or to depict Yae Miko as a sort of "bridge" between the world of mortals (Sara) and the divine (Ei).

This ship isn't very popular in the Genshin Fandom, however, is shipped for many reasons. While it's not too popular, It is most definitely, Ei, Sara, and Miko's most popular poly ship on AO3 and anywhere else. Speaking of which, it currently has 95 works on AO3. A reason for these three being shipped is because some EiMiko and EiSara shippers can't decide on either ship, and so decide to combine the two. EiMiko, EiSara, and YaeSara are each popular on AO3, with over 100 works. EiSara has 1997 works, YaeSara has 220, and EiSara, has 388.

Fandom
FAN FICTION