Nikki is the villain!

After going through chapter 8, Ena said the dark things menifest through Nikki's infinity heart.

Her greed grew the dark monsters around her, she is told to get more mirical outfits to fuel her greed.

I seen enough magical girls anime to see where this is going.

Its this get more outfits to satisfy her greed(impossible because its called infinity) before she turns into the same monster she hunts everyday.

Nikki is going towards a path that only leads to ruin.