Oh, that's so sad that she never told to this timeline Asu that she was raised by him.
In fact this big reveal about Nikaido's magic was quite simplistic:
- She can use her black box to time travel.
- She travaled back in time and changed the past making her friend never be found in the river and die as a baby.
- Then we don't know what happened next, but we can presume that she tryed to fix it, and in the end she just got separated from Asu, but without to recover the timeline her friend existed.
Basically, she had a lot of trouble with butterfly effect of time travel, but Asu said the right thing: It is just because she never learned how to use time travel.
Oh my, from this point the possibilities of the plot are infinite! I really hope the author don't disapoint us. What we will find out? That is still in the limbo.
This is DOROHEDORO