Chen

Chen (첸) is Mei's demon.

Biography
Chen is a snake demon who saved Mei from people who wanted to kill her. Chen becomes involved with Noir at one point, tempted by the idea of "becoming one" with Mei and protecting her in a better way than he already has.

Chen cooperates with Noir by conducting countless experiments on demons and witches, trying to find ways for a demon to gain a new container, or body. Meanwhile, Chen digests other witches' cores in order to stay alive, having since betrayed Mei and not received her witches' energy.

Chen and Noir ultimately succeeds in their experiments, and Chen switches bodies with Mei. Their deaths after the final battle between Suri and Hyojo are implied but not explicit.