I think good horror/thriller are only as good as how long they stay in your mind, and ever since reading this story a decade a go, I've never looked at spirals the same way, whether that may be the shell of a snail, wounded up cables, or a piece of ramen decoration.
You might be frustrated with the leads of this manga. They both are aware of the horrors but choose to not run away. I'm lenient on idiot plots because without them a lot of stories will not happen at all, but in this case, I kind of like their reason of staying. Their reasoning loops around until it ends at the start, like a spiral.
The ending was more or less perfect too.
