TV-Series
Description
Karen is a supporting character who serves as the Mermaid Princess of the Antarctic Ocean and the keeper of the purple pearl. She is the younger twin sister of Noel, the Mermaid Princess of the Arctic Ocean. Despite being twins, Karen and Noel were born on opposite sides of the Earth and had never met prior to the events of the story, though Karen is deeply aware of her sister's existence and cares for her profoundly.

In terms of personality, Karen is initially presented as a mysterious and aloof figure. She is typically calm, mature, and collected, but can act cold and distant toward others, especially the other mermaid princesses when she first encounters them. This cold demeanor stems from a deep-seated misunderstanding regarding her sister's capture. Karen was told by her servants that Rina, the mermaid princess of the North Atlantic, had abandoned Noel to be captured by the villain Gaito. In reality, Noel had sacrificed herself to allow Rina to escape. Because of this false information, Karen harbors a strong grudge against Rina for a significant portion of the first season.

Her primary motivation throughout the initial story arc is the rescue of her beloved twin sister. Karen is fiercely independent and prefers to search for Noel alone, initially refusing offers of help from Lucia, Hanon, and Rina. She states that she does not trust them and believes she must save Noel by herself. This singular focus drives her actions, and she is shown to have been saving the power within her pearl specifically for the purpose of freeing Noel.

Karen's role in the story is that of a reluctant ally who eventually becomes a crucial member of the group. Her debut is marked by a talent show where she wins first prize, which first brings her to the attention of the main characters. She later saves Lucia, Hanon, and Rina from the Water Demons with her powerful singing voice. The turning point in her relationship with the others occurs when she is trapped in a black mist by the Black Beauty Sisters, Sheshe and Mimi. To save herself, she is forced to use a significant amount of her pearl's power, distracting the sisters so the others can escape, which ultimately leads to her own capture. This act of selflessness, along with the efforts of Rina and the others to save her, finally resolves the misunderstanding between her and Rina. After this, Karen forgives Rina and eventually agrees to join forces with the other princesses to confront Sara, the Water Demons, and Gaito directly. The culmination of her personal journey occurs when the group finally locates the captive Noel, and Karen rushes to embrace her sister, referring to her as Onee-sama.

In the second season, Pure, Karen's personality evolves considerably. Having secured her sister's safety, she relaxes, becomes much kinder, and is more open to having fun with the other mermaid princesses. She is shown to have an interest in beach volleyball. During this season, a key development is her love interest in a British glaciologist named Subaru. The two are shown researching a mysterious temperature rise in the Antarctic Ocean. While she cares for him deeply, Karen hesitates to pursue the relationship out of concern that her dangerous duties as a mermaid princess would put his life in jeopardy. She also gains a penguin companion named Pipi who assists her.

As a mermaid princess, Karen possesses several notable abilities. Her primary power lies in her singing voice, which she uses to purify and drive away enemies. She can transform into her idol form, known as Purple Pearl Voice, to perform this ability. Her signature attack phrase is Cutie Hot Pitch. In the anime, she shouts Purple Pearl Voice to initiate her transformation, whereas in the manga she can transform at will without any incantation. Karen can also use the concentrated power stored within her pearl to create blinding flashes of light powerful enough to temporarily repel strong enemies like the Black Beauty Sisters. Physically, she is described as being tall with long, dark purple hair that has curled ends and matching purple eyes. She also has a distinctive birthmark on her right cheek.