Kyousuke Kosaka and his little sister Kirino have never gotten along well with one another much less had a conversation. Kirino has always been caught up in her popularity, studies, and good looks. One day Kyousuke discovers an eroge that his sister was hiding and Kirino finally caves in and admits to Kyousuke her secret life as an otaku with an obsession of "little sister" themed erogo. Afraid of blemishing her perfect reputation, friendships, and career as a model Kirino wants Kyousuke to be her life counselor and help her hide the truth from their parents.