Which makes sense, because the spiral itself isn't some kind of evil entity - it's more of an unknowable entity, with very real ties to the phenomenon of love (Twisted Souls, The Snail, The Scar, Jack in the Box... um... all of them, really). Hence the obsessive behavior of those afflicted (that continues after death), the irresistible draw of the spiral, the self-destruction, the way the spiral twines and intertwines.
Ah, it's great stuff, and I really recommend the series - but be warned there is serious Disturbing Imagery therein, and some of it may hit one of your squick points. I decided to take a break after Chapter 11 (The Umbilical Cord), because that was just viscerally awful, and I had to read like three volumes of Dragonball to get back to my happy place.
* He came up with Tomie, you may have heard of her. He also did Gyo, which I really want to read too, though I suspect it's like incredibly grotesque.