APNS-233 My little sister was made into a fellatio slave by those guys... First Love Nenene.

Brother Ryuta is a half-reclusive individual who has built a sexual relationship with his younger sister, the student Nenene. Although Nenene knows that this is wrong, she cannot refuse Ryuta's kindness and, while they haven't engaged in intercourse for years, they continue to have oral sex. One day, Ryuta's friend from his student days, Kameda, visits them. Kameda has set his sights on Nenene's large breasts and plans to use her relationship with Ryuta as leverage to assault her…