Because I had to attend a short summer course for four days, I decided to stay at my sister-in-law's house. They welcomed me very warmly, but my brother-in-law didn't know a secret. That was, my sister and I had fucked each other! The thing was, before Suzume got married, because she was my sister, she always forced me to fuck her. After a long time of not seeing her, I could see her lustful eyes when she looked at my crotch. And sure enough, as soon as my brother-in-law was gone, she rushed over to touch my cock. I kept pushing her hand away and ran away. But the truth was, I still remembered my sister's body, remembered her big, round, soft breasts, remembered the times I put my cock inside her wet pussy. Just thinking about it made my cock stand up, and I was about to masturbate when Suzume opened the door and walked in. This time I couldn't help it, she immediately showed me her breasts, continuously saying lewd words into my ear to make me hornier. And during these four days, whenever my brother-in-law was absent, she would come back to jerk my cock, let me fuck her breasts, and even fuck her pussy.