When I went back to my wife's parents' house, my sister-in-law and her husband happened to be visiting as well. I was attracted to my sister-in-law's charms, who is more beautiful than my wife, and I couldn't help but stare at her. And I fantasized about doing all sorts of things with my sister-in Kokoro. Then, my sister-in-law unexpectedly seduced me! Even though we are step-brothers, this is incest... My sister-in-law was excited to steal me from her sister, so I got excited and stole my brother-in-law's.