Continuous orgasm incest - mother who keeps cumming

Miku has built a happy family with her husband and son. I wasn't particularly dissatisfied with my current life, but I did have one problem. It was that her nightly activities with her husband, who had been with her for many years, had gotten into a rut. Miku has tried various things to get out of her rut many times, but sex with her husband is monotonous and before she knows it, she is no longer satisfied. At that time, Miku notices that there is another man in this house...