Kyosuke Kosaka (voiced by Yuichi Nakamura), a 17-year-old ordinary high school student living in Chiba Prefecture, has a 14-year-old sister, Kirino Kosaka (voiced by Ayana Taketatsu). However, for a long time, this cute sister has not had a close relationship with him, and sometimes can even be described as indifferent. What happened to his sister? Finally one day, a secret about Kirino was discovered by Kyosuke. The cute sister is actually a brother-con of the otaku? ! Although Kirino denied it in every possible way, the facts cannot be quibbled. Later, the rich lady Makishima Saori (voiced by Hitomi Namatame) and the poisonous girl Goko Ruri (voiced by Kana Hanazawa), who originally only appeared around her sister, gradually surrounded Kyosuke. They are all otakus of the Akihabara system like her sister. Kirino, who feels particularly depressed because of her brother control, will develop a kind of interesting relationship with her brother Kyosuke who controls her sister?