Is it just me or is yayoi acting far more mature compared to the older girl? But I guess that is typical of fiction like this. Real kids aren't interesting to read about so you have to put an adult mind in a child's body. After all, who likes an immature, snotty brat that'd just get in the way? Especially in a setting like this.
I honestly can't get behind eiko at all, she's a crazy B with no appeal, just a generic background character but with the added "bonus" of being self-destructively into almost getting murdered.
I also don't like the male protagonist much, he's just too much of a pushover, his only role is to run around and scream and being handled by yayoi without taking proper initiative in getting better at dealing with the supernatural. He should by all means try to get stronger/get more knowledgeable but he seems to have zero survival instinct except screaming, running when things are almost too late already and being a doormat for ghost and human alike.
Yayoi is the only thing that carries this manga. It would be better if she was the main protagonist instead of the useless guy. Kinda silly to put what can only be described as a side character in the main protagonist position. If it acts like one and looks like one, then it is one.