A first year high-school student, Yoko Nakada (Mirai Shida), who seems to be enjoying her youth, has an older sister Makiko (Yu Yamada) who is an elite bureaucrat. Having graduated first on the list from a famous private university, Makiko works for the Ministry of State Affairs. With the help of her beauty, she is envied by neighbours and is considered an unattainable object by colleagues at work, and also the object of adoration of Yoko’s classmates. However, in fact, Makiko is a woman who says hurtful things all the time, puts down other people and does things her own way. If something is done to her, she fights back. Even if nothing is done, she still fights. It is Yoko who takes the damage most, being forced to be a slave to her sister. She thinks that "my sister is the devil".

However, for some reason, the evil deeds of Makiko turn around and bring happiness to surrounding people. The evil deeds that she has done on purpose and by instinct are appreciated, do good for the world, and in the end she is respected…

"Why does nobody notice the true personality of my older sister?" Despite Yoko’s thoughts, gradually Makiko comes to be called "a friend of justice."

本剧是讲述一名15岁高中生, 中田容子（志田未来饰）的故事。她有一位性格如悪魔的姊姊, 名叫槙子（山田优饰），经常欺负, 捉弄及差使她。但容子依然乐观, 快乐地生活着。

槙子在私立大学毕业后, 在公家机关上班。她美丽而且聪明, 可是性格却令人不感恭维。谁人对她不好, 她一定双倍奉还。在容子出生时, 她只想到将来有一个奴隶让她差使, 为她作跑腿及作出气袋。狡猾的她, 把自己这一面掩饰得天衣无缝, 谁也不知她这「内里」真正的一面。受尽折磨的容子, 大叹上天真不公平。

容子相信上天终有一天会惩罚恶魔姊姊, 可是在这天来临前, 她仍然要像奴隶般, 受尽姊姊的差使。这是一部既轻松又不缺温馨的清新喜剧。