Kirino Kousaka is the epitome of a model student with stunning good looks. Her academic record is impeccable, and to support her personal expenses, she works as a professional model together with her best friend Ayase Aragaki, who dislikes liars and anything related to otaku culture. Unbeknownst to Ayase, Kirino has a deeply rooted secret that will soon come to light. One day, Kyousuke, Kirino's average brother, discovers an erotic game that belongs to none other than his seemingly perfect sister at home. In a bid to protect her reputation, Kirino imposes a gag order on her brother while also introducing him to the world of anime and eroge culture. Through Kirino, Kyousuke meets the gothic lolita Ruri Gokou and the bespectacled otaku Saori Makishima, sparking a whole new way of life. However, as he gets more involved in his younger sister's hidden world, keeping it under wraps becomes increasingly challenging.