Mary "Sea Witch" Read

About

Mary Read is one of the Witches invited to participate in the Walpurgis, she holds the title of "Sea Witch" and her desire is the Oceans. Due to her large size and intimating appearance, one would assume Mary was a frightening and commanding individual. However, Mary is actually quite friendly and affectionate with a love for cute things, as demonstrated when she immediately hugged a demon girl she just met and offered her a chance to join her crew in sailing the high seas.

Despite all this, she seem to have a split personality, as she is the only one who can see and communicate with Annie.

During her time as a pirate, Mary Read and Annie Bonny were best friends who plundered other ships on the Caribbean Seas until they were both captured and imprisoned for their crimes. Annie, due to her engagement, was released early and left Mary to rot in prison. Heartbroken by her friend's betrayal, Mary developed a split personality of Annie in order to cope with the situation. However, over the next six months of imprisonment, Mary's mind would continue to deteriorate further and further until she could no longer distinguished reality from fantasy.
(Source: Majo Taisen Wiki)