Reviewing the overall series here since the installments were so short, I don't feel like going back to write a review for each one. (Spoilers to follow)
This manga started out just as chilling and horrifying as I expected, with creepily beautiful artwork to match. The first half definitely kept me guessing, with a morbid fascination, at how exactly Seiko became the way she was. It was crazy how she could switch from demure to demonic at the drop of a hat. And I was so scared for Seiichi at times I wanted to reach through the screen and save the poor boy from her clutches. The culmination of all the twisted drama was shockingly well done... and then the story just seemed to thin out from there.
For one, the fifteen (?) year timeskip felt too long for me. I wanted to know how Seiichi made it through juvie, how he coped when he was first released, and maybe see him track down his mother and confront her. Because it's hard for me to believe he didn't even try for over ten years. If he did and I forgot it was mentioned, it still has less of an impact when told from a retrospective point of view. And when he finally found her, she was deteriorating with old age and could only provide an underwhelming explanation of her past. It all felt as though Oshimi wanted us to feel sorry for her, but I couldn't. All the abuse and violence were too recent for me to simply follow the artificial timeskip, and I also don't have it in me to forgive and forget a character as evil as Seiko. So that's where my reading ends with this manga, at least for now.
Sure, I'm still mildly interested to find out how it all ends, but how else could it end - Seiko will inevitably die, Seiichi will either remain alone or get back together with Fukiishi by some miracle. But there's no catalyst left to the story with Seiko, the main antagonist, basically gone. It's a shame, because the first chunk of the manga was so tense and terrifying, but all things have to end sometime, I guess.