My mother and son watched an AV: "There's no way I'm excited about this," and at first, my mother was calm, but somehow she couldn't hold back...

What causality or luck? My son ends up watching his favorite AV with his mother. My son gets an erection no matter what. My mother is restless as she watches this situation and her AV screen. Motherhood surpasses rationality and says, "You... you want to have sex now?" and crosses the line, telling herself that it's for her son. "My mother has now become a woman."