Butterfly Juvii evolution chart

If you confuse how the chubby caterpillar turn into a human, here's the story.

 

This caterpillar has ability to adapt or mix themselves into what they consume. And incidentally this cute one while making herself a cocoon didn't know that there's a corpse of a little girl beside it. At lv.10 the cocoon absorb the human life into itself, and became a half human butterfly.

 

She lost her memory of herself being murdered, and wandered in a forest. One day she was trapped into the spider web.

The giant spider injected a poison into her, but luckily she survived. 

But because of the spider's venom inside her, it transform her into a poisonous butterfly. Her memories slowly starts to return and now she's a butterfly beast that one day will find and revenge the murderer.