Sister-in-law's temptation ~Under the same roof with my brother's lewd wife~

I live with my brother and his wife, but my step-sister Karen shows me her intense sex with my brother, and purposely lets me see her taking a bath... My sister-in-law seduces me and I can't control my lust. Finally, I couldn't hold back anymore, and as I was masturbating while smelling Karen's underwear, she suddenly came into the room and asked me, ``What were you imagining while you were doing this?''