I have a half-sister, Mizuno, a beautiful girl with a slim body. Due to the specifics of their work, my parents often go on business trips away from home, leaving the two sisters to take care of each other. When we were at home, we were dressed very comfortably and coolly, and Mizuno didn't even wear a bra. Because we are in puberty, our physiological needs are also very unstable, especially my sister. She often masturbated very carefree without paying attention to me. As a habit, this time she continued to masturbate but forgot to close the door of the room, and I happened to pass by and accidentally saw that scene. Out of curiosity, I watched very attentively and was discovered by her in reverse. She boldly touched the boy, made him erect, and then seduced and entice me to participate in the incest affair led by her.