the ghost is a lot less malicious than expected? I mean, there's the obvious trouble with her more or less hijacking Mayumi's body and actions, but she seems to guide Mayumi to a mostly healthy life minus the revenge killing bit. And especially since the motive is revenge, there's little reason for this to expect that more killings will occur. Also, Mayumi's free will isn't entirely subsumed: she seems to talk with the ghost and has some opinions on things.