My father remarried, and Yuriko came into my life as my new stepmother. She was different from before—beautiful, with a stunning figure, someone I couldn't help but admire at every glance. Still, I found it hard to accept her as a mother. One day, she began studying to obtain a license in oil esthetics. During her training, she asked me to be her practice partner. Wearing only paper pants, I lay down on my back as she straddled me and started applying oil. In that moment, her skirt rode up, revealing her glistening, oil-slicked back, which looked breathtaking to me. And the sight of her big, shapely ass, visible from that angle, struck a deep chord within me.