1stly, they ended it with an ending wide open... I mean like really wide
2ndly, I was too interested in his mom
3rdly, I didn't like the fact that Furuya was like poisoned by Rea for a short amount of time and then just returned to normal. This would be satisfying for me only if it turned out that Rea's not a zombie but something else..
4thly, I am not satisfied how they ended things with her father. After 16 years of his freaky behavior she just tells him that she doesn't like it and that's all it takes to make him into a good guy
I do say these thing but that doesn't mean I didn't enjoy the show... I might read the manga to see what happens next