My father's remarriage partner, Ichika, is almost as old as me. I suspected that she was marrying for money due to the age difference, so I decided to observe her behavior. One night, one month after I started observing, I looked into the bedroom and saw Ichika masturbating. Fueled by sadism, I aimed for a time when my father wasn't around, and began to train Ichika as an obedient sex slave.