After the SPF (Supernatural Police Force) caught wind of Ciel and Puro's little adventures together, Mel decided it was time to finally put Puro to justice. She pretended to be his friend but just as he was about to try and turn her, she got out a capture cube and sucked him inside it. A few seconds later she brought him into the capture department where he was put on trial and found guilty, he was then imprisoned and stripped of his goo powers, turning him from a wolf-creature into a human and his punishment is permanent so he can't turn back, as his memories were erased and new ones were put in.