My older sister, who is much older than me, came back after a few years. She still treats me like a kid, even though I'm a student, and forcefully invites me to take a bath with her... "You won't be popular unless you keep me clean." She's so caring that she even peels back the foreskin and washes it for me, but my cock is getting bigger and harder than it used to be, and she looks at it with a dirty look, and I ejaculate unexpectedly when she washes it with her hand! My cock has grown into an adult since I last saw it, and my older sister is getting horny for the man juice, so we cross the line between brother and sister and become a man and a woman...!