I liked them all.
I didn't think I'd like Haru as much though, given her general spunkiness and fangs. Losing her power did a lot in the process though. Now she makes egg bento instead of zombie salad.
Yuu's character development was unexpected by me, but not at all unwelcome.
So far, I'd say Sera is the least likeable of them all, but not in the hate book by far. Depends on how much more she abuses the guy actually. I gave Haru an episode, after all.