Although I won't go too much into details, so as to avoid major spoilers, I have to say that right until literally just a few minutes before the end of the last episode, I was pondering within myself whether I was gonna give this a 9 (or more probably an 8, 'cause it did have its faults anyway - more on this in a while), but then imho the writer decided to ruin everything just for the sake of a silly, shallow, "hollywoodian" final scare. If I ever rewatch this, I'll make sure to stop watching before that point (just as with an American TV series I liked as well, but only except the very last minutes, "Point Pleasant" - but that's another story).
Too bad, 'cause otherwise this dorama could've been a much better one, more coherently Japanese (in that horror is used also to convey deeper moral messages), despite the fact that it still had some script problems (most of all, the inconsistence in some characters' behavior - namely, the FL's BF and the mom - but also the fact that it had too much going on for only 7 episodes, and the writer wasn't able to wrap everything up nicely anyway).
Acting wise, another great performance by the lovely Shiraishi Sei and Kuroki Hitomi, whereas the rest of the cast was ok but nothing to call home about, imho. Direction, photography and music were also OK.
All in all, if you're a fan of Japanese horror, a pleasant watch.