Kanojo no Imouto wa Nikushoku kei Gyaru

The main character is invited to the house of his senior, Arisa, whom he is dating, but is left alone in her room to go shopping. As he masturbates in the underwear he finds in her room until she returns home, he is seen by her sister, Sara, a black gal! She hides behind Arisa who comes back and he does all kinds of naughty things with her sister! 1-3. Kanojo no Imouto wa Nikushokukei Gal (My Girlfriend's Little Sister is a Carnivorous Gyaru) 4. Docchi ga? Docchi mo? Oneechan!? 5. Omake