Brother tricking sister

I have a story idea. A guy invents headphones that when placed on someone's head and they focus on the music or something else they will not notice if somebody is doing something to them unless they see what's going on. So when his twenty something sister's headphones break he gives her his set. At first he only does little things. Then he invites different family members. One day when she's laying on her stomach and propping herself up on her elbows they move on to sex with her. It goes on for a while. She doesn't seem to notice anything except some changes in her body. One day she looks back and sees either her brother or someone from college having sex with her. After that she discovers she's had sex with a lot of her male relatives, some female relatives, and some people from school. You can change it so she has had sex with more or less people. As long as some incest is still there. But eventually the brother discovers that the headphones don't work, not in the way he intended. His sister was aware of most of the stuff. Just not the small stuff like pinching or light touching. But it did help her to pretend she didn't notice the other stuff.