Oreimo follows the daily life of an ordinary high school boy named Kyousuke Kousaka. Kyousuke’s younger sister Kirino is a pretty fashion model, but also hides a dark secret of being an otaku of adult games. Kyousuke is the only person to whom Kirino reveals her hidden obsession and other issues.
Kyousuke brings Kirino home from America where she attended a special track & field camp. Surrounded by her friends, Kirino gradually gets her life back to normal. In stark contrast to her friends is Kyousuke, who is unhappy with Kirino's attitude towards him. She has been ignoring him since she came home, as if their relationship had gone back to how it had been a year earlier.