Kyousuke Kousaka, a normal 17-year-old high school student, hasn't gotten along with his younger sister, Kirino (14) in years. For longer than he can remember, Kirino has ignored him or looked at him with spurning eyes.
One day, Kyousuke finds a DVD case of a magical girl anime laying in the entrance of the house. To his surprise, inside is an adult video game titled Love with Little Sister!
That night, Kirino bursts into Kyousuke's room and in the first conversation she has initiated with him in years, says they have things to talk about. Kirino brings Kyousuke to her room and shows him the collection of moe anime and lolicon bishoujo games she has been collecting in secret.
Revealing herself as an Otaku, Kirino begs her brother to help keep her frowned upon lifestyle a secret from their judgmental Father, a policeman.