She's Koyomi younger and Tsukihi older sister. She is a self-proclaimed "hero of justice" who often imitates the personality and quirks of various characters from tokusatsu series. Despite this, she is completely uninvolved with the supernatural. Befitting her name, Karen is a hot-blooded girl who acts as if she is a superhero who has the duty of protecting others from danger. When she was in elementary school some of Koyomi's thoughtless words nearly drove her to commit suicide. It was then that she started becoming an ally of justice. She states that it was Koyomi who created the "hatred of evil in her heart". She likes to imitate characters from various tokusatsu live action series like Dekaranger. Fortunately, she manages to pull it off due to her flexibility and quick reflexes, which are a product of her constant exercise and training, which involves practicing karate and capoeira, among other martial arts. Her personality often collides with Koyomi's more laid back personality more recently, especially since Koyomi has developed a certain degree of anxiety over his sisters' safety due to his experiences with the supernatural. In fact, he has called Karen's habit of acting like a superhero alongside her sister a "travesty". Along with her sister, Karen does not believe in the supernatural. At times, she acts like a bit of an air-head. She is 15 years old.
