I was worried that I couldn't satisfy my wife because I was too premature to ejaculate, so my sister-in-law Nanami saw me training my penis with a masturbator. When I explained the situation, Nanami said she would help me overcome my premature ejaculation. From then on, I began training my penis with Nanami's handjobs, hiding it from my wife. Nanami was also so enthusiastic about training that the acts escalated to kissing and blowjobs... and eventually we even promised to put it in her pussy if she could hold out for 15 minutes. I wonder if she'll hold out and put it in her pussy! But if we unite, it would be cheating... Ahh, I want to put my penis in my sister-in-law's pussy and get all my semen out!!