I'm surprised I've not heard of JVA, albeit East Asian content is normally well down my usual search list.

On the incest thing, I heard years ago this doesn't happen due to a scent thing. We are only attracted to people with a different system configuration to ours that would be beneficial to our offspring. All of that is indicated by scent. That doesn't necessarily explain why we all want to sleep with the same handful of people, but it can explain why incest isn't a thing for the overwhelming majority and why we can all find some people surprisingly appealing in-person.