My cute younger sister, having no boyfriend, was uncomfortable around men and anxious about male patients during her clinical training. She especially dreaded unpleasant tasks like shaving and examining male genitals. To avoid these, she asked me and our father to be her practice partners. As a result, I became her practice subject—she shaved me, touched even the underside of my testicles, causing me to get an erection involuntarily. Later, she requested help from our father for bathing assistance practice. Since she wasn't used to seeing male genitalia, she wanted to examine and wash it thoroughly. Both me and our father carefully assisted her, which eventually turned into an intense handjob. This led to practicing semen collection, simulating a real ejaculation examination. A forbidden relationship began between my sister and me, culminating in ejaculation.