OreKou follows the story of the light novels, set at the time when Kirino Kousaka leaves for America to undergo athletic training. While the OreImo anime series tells the story in Kirino's elder brother Kyousuke's point of view, OreKou focuses more on Kuroneko's experiences as Ruri Gokou, a high school freshman who becomes Kyousuke's junior. While Kuroneko struggles in mingling with her new classmates, she tries to sort out her feelings for Kyousuke.
- Ruri Gokou (五更 瑠璃, Gokou Ruri) - a freshman student of Chiba Benten High School and an otaku with issues on socializing with others. After a long time of staying at home to take care of her sisters, she decided to continue her studies, and ends up becoming a junior of Kyousuke Kousaka, a close friend of hers.
- Kyousuke Kousaka (高坂 京介, Kousaka Kyousuke) - a third year student of Chiba Benten High School and a seemingly "normal" guy who ends up entering the world of an otaku because of his younger sister. He has been friends with Ruri for some time, and he now acts as Ruri's usual companion in school.
- Kirino Kousaka (高坂 桐乃, Kousaka Kirino) - a second year student who is currently in America undergoing intense training in track and field. She is an avid fan of eroge that features romantic relationships between siblings and the one responsible for his older brother Kyousuke's exposure to otaku culture.
- Sena Akagi (赤城 瀬菜, Akagi Sena) - Ruri's classmate in Chiba Benten High School and a member of the school's Game Research Club. She hides her interests with male-to-male romance from everyone, but ends up exposing this to everyone in the club. She was initially in bad terms with Ruri due to a clash of egos, but eventually became friends with her after certain circumstances.