It's more like people are complaining not because it's that bad, but more like it's worse than what the manga was or what it could be (at least that's the case for me)
I too, still enjoy the story, although, it's certainly not the best
The paper (according to these church guys) only enchanced her vision as she lost one of her eyes
It's the flower which makes her lose all control
However, I don't know if she always had this urge to kill before, but with self-control like every normal person, or it was instilled in her
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