Kōi Ou is a student in the anime Cheating Craft, identified as an L-type, meaning she follows the Learning path, prioritising study and academic effort over cheating. She is a beautiful young woman with cyan hair and orange eyes, stands about 161 cm tall, weighs around 43 kg, and her birthday is on July 7. She always sits at the very front of the classroom and is an exemplary L-type student, known for her strong dedication to honest study. Her personality is principled and hardworking; she holds a deep dislike for C-type students who rely on cheating to pass exams, viewing them as dishonest and undeserving. Despite this, she develops respect for the protagonist, Mumei Shokatsu, because he achieved a perfect score on the entrance test without being caught cheating, even though he is a C-type. This respect forms the basis of an unlikely partnership. Her primary motivation is to succeed academically through legitimate means, but she is forced to cooperate with Mumei and other C-types as the exam environment becomes increasingly competitive. In the story, she serves as the L-type heroine, working alongside the C-type protagonist to navigate high-stakes examinations, often clashing with him over methods while gradually learning to trust his skills. Key relationships include a developing alliance with Mumei, and interactions with fellow students such as Rinu Shu and Haku Ryu, as well as Teacher Oh. Throughout the series, she undergoes subtle development from strictly opposing all forms of cheating to begrudgingly accepting that collaboration with C-types is necessary for survival, though she never abandons her core values. Her notable abilities lie in her academic prowess and disciplined study habits, making her a top performer in pure learning-based challenges; she does not use any special cheating techniques, relying instead on memorisation, preparation, and quick thinking.