Overview:

Summer vacation. While his parents are abroad, Takuma lives with his younger sister, Hiyori.
Hiyori used to be obedient and cute, but recently, she has become a bit cheeky.
Takuma wishes that Hiyori would return to her old self, but Hiyori’s cheeky behavior only escalates. ……
Finally, Takuma runs out of patience and decides to train the cocky bitch …… Hiyori and make her understand and return to the honest Hiyori.​