My brother's wife, who lives with us, is defenselessly showing me her lewd body, and I get so turned on by it that I can't control myself anymore, so I pretend it's a coincidence and get close to my sister-in-law and rub my rock-hard cock against her. She doesn't seem to mind, and she starts squirming, so even though I know it's wrong, we keep quiet and fuck each other secretly so my brother, who is nearby, doesn't find out.