Interesting so I was right with my theory last chapter, so whenever we see Kaya's eyes change when she uses her powers we are in fact seeing within the shell at the spectre inside the shell or perhaps its the spectre looking outside of the shell that we are seeing. I think its a case that the Ebisumori spectre is actually passed down from priestess to priestess each one serving as a host until the next eldest daughter is born and that something went wrong with Mirai either before or during her first pregnancy? Also is Nana the eldest daughter or is Mirai? Because it seems to be family tradition to have whoever happens to bear the spectre at the time to enter into and carry the "family business" of being a prominent psychic as it were... yet Mirai didn't and her child acquired it while Nana did enter the business and seems rather weak in comparison to Blindma. So did the family spectre rebel in some way leading to Mirai's secret birth and it passing to Kaya, Namu is Kaya's uncle, or did some outside factor cause this to occur? By part of the spectre remaining in the womb and taking a second simultaneous host these has me feeling the spectre is rebelling against the Ebisumori, that would explain grandma's rambling in her room upon meeting Kaya, or it could be something else taking advantage of the situation so it can access the Ebisumori womb gateway. I also like the parallel between what the Ebisumori have been doing for generations and what that evil organization in Dark Gathering also does.
Thank you for the chapter.
Also I do think that the family spectre has another personality outside of the surface Kaya personality that does manifest from time to time as seen in the reunion scene in grandma's room in the nursing home and when Chie hugged both Kaya and Sakuya after the store room incident I think the pardon the pun "Kaya shell persona" is just the result of how the spectre's been raised while in this current vessel like a somewhat normal 5 yr old girl but below that is that original mind of the generations old entity.