Watching the movie, it seems like there is some relationship between the Cursed Blood Clan (CBC) (Kuriyama's) and the Kyoukai no Kanana (KnK) Youmu's origin.
And I am not talking about the romantic relationsip between Mirai and Akihito. About the origins of them both.
It is shown that
Akihito and Mirai's mothers were close enough that Kuriyama could ask to be reforged into a ring upon her death.
So, what is the rellationship?
Was the CBC involved in creating KnK?
