This fan art came out after Cookies' Dream story update.

※ Fan art spoiler :
Black Pearl Cookie's past is revealed in Oyster Cookie's dream: She was originally a good mermaid. She fell in love with the ancestor of Oyster family and gave her pearl as a gift to him. But Oyster Cookie's ancestor betrayed Black Pearl Cookie and provided the cause of her personality breakdown; She eventually took away the "precious(life-valueable friend's pearl)" of a friend mermaid passing by, and she was cursed, lost her power, and sank into the deep sea to become the current Black Pearl Cookie.

• "precious": There is a mention that the pearl of the mermaid is like a spirit stone, and the pureer the cookie's heart, the brighter the mermaid's heart. According to the story, she tried to take the pearl from her life-valueable friend to give to the ancestor.