The younger brother, who is studying for his entrance exams, is currently worried that he can't concentrate on his studies because he sees his older sister in a sexual way. When his sister points this out to him, he decides to beg her for sex...but of course she refuses. But the younger brother doesn't give up and suggests, "If you can't do pussy, let me lick your asshole!" The older sister reluctantly accepts, but gradually she becomes addicted to having her asshole licked...her body can't stand it without her brother's asshole licking!