17-year old high school student Kousaka Kyousuke was at a cold-war with his little sister Kirino. They seldom talked and never had a proper conversation these past years. One day, Kyousuke accidentally finds a DVD case of a childish anime program titled "Stardust Witch Meruru." What surprised him more was the fact that inside the case was an R-18 Ero-game CD ROM. Things looked bad since the obvious suspect for having pornographic material such as that was HIM. (He did have some, but they were all magazines.) He didn't want to think what would happen if his mom or his scary father found out about that. Later, he learned that his little sister owned the DVD case (AND the CD ROM inside). She confessed to him that she liked, er, loved Imouto characters with great passion, enough that she'd bought tons of Imouto Ero-games and other Imouto-related items. To put it simply, he learned that she was an Imouto-only Otaku. Kyousuke had hard time believing that a "typical girl nowadays" such as his sister would turn out to be an Otaku. Now, Kirino wants Kyousuke to have a "life consultation" with her, which put an end to the peaceful life that Kyousuke was having.