Having to attend a short summer course for four days, I decided to stay at my sister-in-law's house. My brother-in-law and sister welcomed me warmly, but little did he know a secret... that my sister and I had sex before! Before my sister Suzume got married, as the older sister, she always made me have sex with her. It's been a while since we last met, and I could see the lustful look in her eyes when she glanced at my crotch. And indeed, as soon as my brother-in-law left, she rushed to touch my cock. I kept pushing her hand away and ran off. But the truth is, I still remember her body, her big round soft breasts, and the times when I inserted my cock into her wet pussy. Just thinking about it made my cock erect, about to masturbate when Suzume opened the door and walked in. This time, I couldn't avoid it anymore, she let me admire her breasts, whispered seductive words in my ear to make me even hornier. And for the next four days, whenever my brother-in-law was away, she would come to jerk me off, let me suck her breasts, and even let me fuck her pussy!