@Nogoodimaginativename I have different theory, I think her mother is the one who sealed her power and when she live with Kudou, she already fulfilled some part to unseal it.
My theory is that Miya's mother sealed her ability and influenced the way her father treated her with her abilities because Miya's mother knew that she had limited time left in the world and that Miya's father would marry his old lover again when she died, and that the stepmother would mistreat Miya after he remarried. So she sealed Miya's abilities so that Miya would not be used for her abilities by the saimorri's(?). And that the effects of the spell would fade away when she was in a new house/clan where she is going to be safe and happy
Correction to the note at the bottom of page 24: Miyo's mother's background is first brought up in chapter 7 (pages 21–24; including their name and a little more detail about the family itself and their powers).
@Master123456789@Nogoodimaginativename@katakatakara@Nunally
That theory doesn't quite make sense, considering ability-less people in ability-using families generally get treated really, really badly. Her mother would also have expected that Miyo would be treated poorly without her powers, especially considering the way her father was already treating her at the age of 3 or 4. Not to mention the problem of how a power might be sealed to begin with. The fact that Miyo's dreams are the result of a power is even more clear in the novel, where it is explicitly mentioned that Miyo was not present and therefore is not a memory (the one where her father said that he would have loved Miyo if she had powers). As for the reason the dreams are occurring in the first place:
Aside from the possibility of her mother trying to keep Miyo safe from something or other, it's far more likely that Miyo's powers being sealed or semi-dormant has to do with the Usuba family itself or the nature of what ever her power is. The timing obviously has to do with getting treated like a human being rather than a slave, though. From what of the novels has been translated thus far, this seems to be even more likely (but nothing has been confirmed). The only thing that has been confirmed is that her mother ran away because she was basically going to be used as a breeding mare, since the children of people with her own ability have the strongest ability of those held by the Usuba family. Whether this is actually the case for Miyo… hasn't been translated yet.
I think that Miyo is so traumatized that she might have used her innate ability against herself, which strengthened her belief that shes incompetent and useless