A father and his sister move into a new house. Unlike their previous home, the house is small, and when the brother and sister share a room, the brother begins to think of his sister as a woman. His sister's slender bare legs, her panties flashing, and his eyewitness seeing her masturbate. His sister's body, which he didn't even notice, stimulates his brother in a fascinating way. And the brother can't bear it anymore... This is the story of a week until a sister and brother become female and male.