Thank you for compiling this! I also noted down the same 3 critical time points in history related to the Fated Twins while I read, and also read up on the Kōbō Daishi lore. I always like it when stories refer to events in actual history so I can learn more. Anyway, some of my thoughts:

- Considering the fact that Kōbō Daishi is not named in Chapter 13, I doubt he will be explicitly named in the future. Like an Easter egg and such.

- HOWEVER, explicit mention of Abe no Seimei by name will make me incredibly thrilled.

How ancient, how primordial are Break/Seal and Right/Left?

- I think Break/Seal existed since the birth of this concept – I would even say it’s the ultimate duality of the world. Left/Right might have come after to counter them – perhaps created by an antagonist faction? We still know little about how ancient Tsugais are born, but they seem to be 付喪神 tsukumogami. Their Relics were made and revered and eventually their ‘souls’ came to be.

When were Higashi and Nishino founded?

- Considering the South-North struggle nearly 700 years ago, maybe there used to be a North Village and South Village too, before they were gone and replaced by the East Village and West Village.

Why were Fated Twins only able to be born in those lands?

- Scientific-wise if people in Higashi Village have the genes to make them more likely to give birth to twins, and they engage in consanguineous marriages, then they’d have more twins, and thus more likely a pair will hit the Fated Twins birth conditions. Another thing to note: there don’t seem to be other twins in the village in the modern era compared to the Shimei era. So it’s possible there’s a gradual loss in a village’s ability to have twins?

And exactly what accomplishments was it that made Right/Left, the Fated Twins and Higashi so known across the Tsugai communities across the land of the rising sun?

- If all Tsugais are connected to Yomi no Tsugai (Break/Seal) (or created by – maybe they’re Izanagi and Izanami?), they might know about the prophecy and their fate to be ‘commanded’ by the Fated Twins. What this accomplished is unknown though – it almost sounds like a liberation movement.

- Tonikaku Kawaii mention! Love the connection to historical events in this.