Kono Kankei wa Gouhou Desu!

YES Sister, NO Touch! Kouta, who is extremely siscon, decides to live alone in order to "escape from his little sister ". One day, however, he picks up a runaway girl named Ui, who is full of younger sisterly feelings. Although she looks and acts like a child, she is in fact a beautiful 19-year-old girl with big tits! Protect his sister? or Crossing the line? The days of agony begin!