She is younger sister of Xenos, a gladiator at Granshill. She is a gentle girl who wants to be helpful to others, therefore she is a nurse at Rashell clinic and studies medicine. There is no one else who knows medicinal plants better than she does, and she makes use of it at the health preservation clinic. She often goes outside to forests to collect medical herbs. She originally decided to learn healing for her brother Xenos, a mercenary, who doesn't cease to get injured. She often worries about him because he does dangerous work. Xenos took care of her when she was a child after their father went missing and their mother died.
Her appearance is gentle and sweet but when it comes to working at healing a patient, she shows a surprisingly strong heart. Her personality is reserved and she tends to keep her heart closed toward anyone other than her brother. Although she is self-taught in pharmaceutics, she is embarrassingly modest about her expertise.
She is often pursued by bandits and needs to be rescued. Xenos is protective of her and sometimes she dislikes being treated like a child from him. When she was attacked a second time by bandits, she had to stay at Rachel clinic to recover. Irene, a Growsian and nurse at the clinic, took care of her and Karen deeply respects Irene.
Karen was kidnapped by Gamuran's subordinates and held hostage to make Xenos work for Gamuran. Gamuran bound her with a spell that could hurt or even kill her instantly. Carmaine's party however found a way to release the spell with Magic Academy vice-chancellor Bradley's help, and they rescued her.
She is daughter of Belgar and his second marriage partner, therefore she and Xenos are half-siblings.
Using her experience as a nurse at Rachel clinic, she remodeled her home in Grandshill to open her own small clinic to take care of people who are too poor to afford health expenses.
She was commissioned to write a book on medicinal herbs by the Magic Academy. She briefly met Wein when he visited the Magic Academy. Karen happened to witness "Maximillian", who was actually Patrick, destroy the dam at Rolandia falls. Because she saw the messenger, Wein went to find her to help prove his innocence. She wasn't at her home in Grandshill and instead Wein found Xenos. She was pursued and captured by mercenaries who were hunting bounties on Wein's party. She was held hostage but rescued by Wein, Xenos, Hans, and Charlone.
If the protagonist does not rescue her from Gamuran, she will die.