During a long holiday, I returned home to visit my family and became frustrated upon discovering that my sister was still living as a NEET, having nearly drained our family's savings. Unable to hold back, I started lecturing her, but she ignored me and retreated to her room. Losing control, I impulsively attacked her. Though initially bewildered, she quickly became shockingly lewd—moaning loudly and writhing beneath me, leaving me stunned by her response. From that night on, our relationship changed completely, spiraling into a series of intense and abnormal encounters throughout my short stay, culminating in a shocking series of events.