When Kodaka Hasegawa finds out that he will be transferring to a new school, he is determined to make a positive impression, and maybe even some friends. However, Kodaka discovers he is out of luck when he immediately gets labeled as a violent delinquent due to his blond hair and intimidating expression. Although a month has passed, Kodaka is still alone thanks to his notorious reputation. However, his life begins to change when he finds fellow loner Yozora Mikazuki talking to her imaginary friend in an empty classroom. After sharing stories of their lonely high school life, Kodaka and Yozora decide to overcome the difficulties of making friends together by starting the Neighbor's Club. Created for people who don't have friends, daily activities involve learning social skills and how to fit in, which will hopefully allow them to make friends. Joined by the eroge-loving Sena Kashiwazaki, and other eccentric outcasts, Kodaka may finally have managed to find people he can call friends, in this club filled with hilarious oddballs.

Unaired 13th episode released on the 7th DVD/BD.

Kirino Kousaka embodies the ideal student with equally entrancing looks. Her grades are near perfect, and to cover her personal expenses, she works as a professional model alongside her best friend Ayase Aragaki, who abhors liars and all things otaku. But what Ayase doesn't know is that Kirino harbors a deep, entrenched secret that will soon be brought to light. At home one day, Kyousuke, Kirino's perfectly average brother, stumbles upon an erotic game that belongs to none other than his seemingly flawless little sister. With her reputation at stake, Kirino places a gag order on her sibling while simultaneously introducing him to the world of eroge and anime. Through Kirino, Kyousuke encounters the gothic lolita Ruri Gokou and the bespectacled otaku Saori Makishima, thus jump-starting an entirely new lifestyle. But as he becomes more and more involved in his little sister's secret life, it becomes that much harder to keep under wraps.

The true end arc of Ore no Imouto. These four episodes branch out after the 11th episode of the main TV series and present an alternative version to the end of the TV series. These episodes contrast with the good end arc of the TV series, which was an original ending written for the anime, and instead closely follows the original story from the light novels.