Even before we got married, I often hung out with my wife's younger sister, Rei-chan. I thought she was cute, but I never thought of her as a member of the opposite sex. Until that day... One day, three years after I got married to my wife, I had a fight with her and left the house, and ended up at Rei-chan's house with nowhere to go. "Hey... why did you marry my sister? Why not me?" I thought she was joking, but then Rei-chan boldly seduced me... and I couldn't refuse.