I became the practice table for my big-butt stepmother who started doing oil beauty salons

My dad remarried and my new mother came. Unlike her previous mother, Yuriko is beautiful and has a great figure, but I was unable to accept her as a mother. One day, Yuriko, who had begun studying to get an oil salon qualification, asked her to become a practice float. She straddled me, lying on my back wearing paper pants, and as Yuriko's skirt began to apply oil, she lifted up her oil-grilled butt approached me in front of me...