Returning to my hometown for the first time in a while, I decided to visit a nostalgic public bath. There at the counter was 'Aika-neechan,' who used to play with me when I was little. "You've grown, haven't you?" she said with the same friendly smile as back then. It seemed like they were about to close, but she let me in specially. As I was soaking alone in the big bath, my older sister suddenly came in. "I have to finish up the closing work," she said, starting to clean. There I was, completely naked washing myself, while a scantily clad woman cleaned the bath. It was a strange sight.
Moreover, my sister's white shirt during cleaning was soaked through with water, clinging tightly to her skin. Her large, bra-less breasts were visible as if through a lie. Noticing my gaze, she brought her see-through breasts, with even the pink color of her nipples visible, close to my face and teased me, peering into my eyes. "You've become a man, haven't you?" she said, seeming somehow pleased, and began to touch my now-erect cock. Before I could stop her, she started moving her hand up and down, stroking it.
When I said I could touch her wet, see-through breasts that I'd always been curious about, my gripped cock grew even harder. Seeing this, my sister grinned with amusement. "You can't cum yet, okay? (laughs)" she said, gauging my reaction, then took my cock into her mouth and licked it with lewd sounds. She also gave me a titjob with her big, soft breasts. When I couldn't hold back anymore, she laughed and said, "I guess I have no choice," and let me have sex with her. But once I inserted my cock, her eyes grew hazy, she let out erotic moans, and she transformed from my sister into a woman. That version of my sister was so incredibly sexy that I ended up having sex with her many times.