When first appearing around Lucia, Hanon, and Rina, she was seen as a loner who had captured Taro's attention, much to Hanon's anger. Towards the beginning of the anime, she is rather cold and distant, similar to Rina, because of Noel.
Despite that Noel and Karen were born on the opposite side of the Earth, Karen cares about her sister more than anything, up to the point of attempting to save her alone. In the second season, she is wild, humorous, and even a bit strange.
Karen fell in love with a British researcher named Subaru because he cared about the South Pole just as much as she cared about protecting the Legendary Glacier and her kingdom. It is believed that Karen may had fallen for Rina's boyfriend, Masahiro in Pure episode 20, but it went downhill when she realizes that he was talking about Rina.
Karen is like a complete opposite of her twin sister Noel from appearance, color, and personality.
- Human Form: Karen has dark purple waist-length hair with the ends curled. Her eyes are brown and she has a mole under her left eye. Karen's wardrobe consists of purple and yellow garments.
- Mermaid Form: Karen's hair is a lighter shade of purple and her eyes are purple as well. Her hair is body-length and is a lot more curly and wavy than her human form hairstyle. She wears a light purple shell bra and her tail is light purple.
- Idol Form: Karen's idol form is similar to Noel and Hanon's idol form, minus Hanon's skirt. It is a form-fitting short white dress with purple trim with frilly purple gloves and boots. She has a small side ponytail tied up on the left side of her head.
In the anime, Karen shouts 'Purple Pearl Voice!' to transform. In the manga, she can transform at will with no incantation. In her idol form, like Lucia and the others, Karen can use her singing voice to get rid of enemies. In manga, at the end of her songs, she uses 'Cutie Hot Pitch' whereas in the anime, she uses 'Love Shower Pitch' like the rest of the mermaids.
- Caren is usually referred to as Karen.
- Karen means "Beloved, Pure"
- She is the purple color of the rainbow.
- She is the youngest twin of Noel.
- She has a mole under her left eye.
- Her bangs swing to the left.