After my parent remarried, I ended up with a much younger stepsister named Ai. I found myself constantly captivated by her studying in the living room. Her accidental panty flashes drew my gaze, and before long, I developed a growing interest in her underwear. One day, while secretly checking Ai's panties, she caught me in the act. She stared at me with a mix of shock and anger—but in her eyes, I also noticed something unexpected: a hint of pleasure.