Kou Yasaka is the president of the Animation Research Club, and is also the treasurer of the Student Council. She is called "Kou-chan-senpai" (こーちゃん先輩, "Kou-chan-senpai"?) by her juniors, including Hiyori, who is a member of the Animation Research Club. She is studying at Ryouou High School in class 2-F and is the only second year among the Lucky Star girls at the time of her appearance (the rest being either first or third year students). She enjoys playing anime-themed fighting games, and also likes to check on new and trendy things, never failing to miss one. She has played fighting games with Konata before, and does not notice that Konata is her senior. She has tanned skin, and likes doujinshi, manga, observing people, chatting, and gambling. In Lucky Star: Ryouou Gakuen Outousai, she is a good friend of Yamato Nagamori.