Congratulations On Becoming A Working Adult! A Sister And Brother, Who Are Moving To Tokyo For Work, Try Taking A Family Bath Together For The First Time In 10 Years, With Only A Towel Between Them! They Shouldn't Be Conscious Of Each Other As Members Of The Opposite Sex, But They End Up Bathing Together In A Tiny Bathtub! The Extreme Mission Makes Them Aware Of Each Other And The Close Brother And Sister End Up Having Unprotected Sex!