She didn't have a cute little sister—she had a younger brother. He was what people call a femboy, and his affectionate, clingy attitude toward me was incredibly adorable, making him someone I couldn't help but be drawn to. This younger brother, Rui-chan, would boldly expose his erect cock and seduce me without hesitation. Right beside his sleeping sister, I experienced sex with him, overwhelmed by both taboo excitement and intense arousal. When she was away, the two of us gave in to our feelings and made love in our own private moments. This deeply intimate relationship would soon become the catalyst that shook her heart to its core.