I'm fine with Japanese fascinations with incest, I guess I'm used to it now. But recently I happened to show an episode of an incest anime to a friend who has no exposure to anime (the plot involved a sister coming on to her brother, but it was a rather tame episode and they were stepsiblings to begin with, with no blood relation) and that did not come across well. Or at all. My friend was extremely shocked. I've been accused of being sick in the head and in need of counselling, and this came from my best friend who I've known for almost twenty years. I thought the reaction was completely over the top.
Needless to say, I am now far more discerning about what sort of anime I expose my friends to
I am really curious about how the topic of incest in anime is perceived by Japanese with limited or no exposure to anime. I want to chalk this up to differences in cultural values, but I would not be surprised if the reaction was similar to what I got. Especially concerning siblings and/or stepsiblings, as cousin incest is a more washed out topic.