Kimeseku Namaiki Sister Kusurizuke!

The two siblings live alone without their parents. The younger sister, a bratty 6th grade junior high school student, often teases her older brother and enjoys watching his reactions. When he reaches the end of his patience, he plans to use an aphrodisiac to turn her into a masturbation pet. Once she allows herself to be fucked, there is no stopping her. The sex with her brother becomes more and more intense, and the sister's body and mind are corrupted by the unlimited pleasure of the aphrodisiac... (Source: Melonbooks, translated) Note: Released at Comiket 95.