Onii-chan, Oshiete... ~Gimai to Himitsu no Hoken Jisshuu~

It reminds me of yesterday. "Use my body as a teaching material for health and physical education!" My younger sister, Yuri, attends a prestigious nursing school. I thought she was on a smooth path to becoming a nurse, but it seems that "when she studies things like men's bodies, her mind goes blank." But, what do you think about using my body as a teaching material for practical training? Is it okay for siblings to do something like that? Even though we're not related by blood... Before I could gather my thoughts, my sister came home. It was as if she had forgotten about last night's promise. I was secretly stroking my chest with relief, but... "Um, um... Big Brother. Tonight... please have health and physical education class with me..." I nodded, swept away by her words. I wonder what will happen tonight. Thinking about it makes my heart beat faster...