My mother-in-law, Ayaka, suddenly became a stepmother when my father remarried. She was beautiful, bright, and had great style, and was too stimulating for me, a virgin. By chance, she found out that Ayaka was a slut in the past, and when she asked him to give up her virginity while sitting on the ground naked, she unexpectedly agreed, saying, ``It's only once.'' I intended to fuck her only once, but it felt so good that I fucked her over and over again, and gradually Ayaka's dormant slut instincts awakened, and she became a complete masturbator.