The beautiful 20-year-old girl Yui Nishikawa from the countryside came to the city to visit her father, but she unintentionally caught the attention of her stepbrother from another mother. Yui Nishikawa stayed at home and behaved, but she dressed provocatively and innocently, causing her stepbrother to be constantly aroused whenever he saw his own father's daughter. And "proximity breeds fondness", taking advantage of their father's absence, the stepbrother seduced his stepsister into the room and tried to engage in adult activities with her. Luckily for the young man, the girl was just as promiscuous...