My Little Sister's Friend

Min Soo is at home since his discharge from the military. His sister, Soo Min, and her friend, So Ri, come home. Min Soo is surprised to see the 'little girl' he once knew had grown up to be such a mature young lady. One day, Min Soo is watching porn when he runs into So Ri. He freezes, but So Ri seduces him, "Want me to satisfy you?"
(Source: HanCinema)