Aoi is the eldest daughter in a family with two siblings. She is very doting and loving towards her younger sibling. However, perhaps because he is the only son in the family, her younger brother has a very stubborn and rebellious personality. One day, when he suddenly passed away, she found her brother using her phone to view explicit content. Instead of scolding him, Aoi encouraged him and practiced with him in person. In the days that followed, the two siblings became closer, engaging in intimate activities throughout the house, regardless of their indifferent father's presence.