I do like stories where otherwise faithful girlfriends or wives are stolen away and/or become sex addicts. At the beginning of the story, it always seems like the women are in a [seemingly] happy relationship. I always find the scenarios, in which they are seduced and stolen by the antagonist, fascinating, though often unrealistic. In some cases, the antagonist shows off his big dick and that's all it takes (this is typical when the antagonist is an AA). Most times, the NTR is kicked off with forced sex of some kind, either through threats & intimidation, blackmail or even rape. This is the hardest part to watch and I usually skip over this part. Despite this, however, the woman quickly come to love the sex and falls in love with the antagonist's dick and out of love with their SO. It is also interesting to see the reaction of their SO as they are losing their women. In some cases, they are totally ignorant of what is going on. In other cases, they know exactly what is happening, but seem to do nothing to stop the process. In a few cases, they even watch their wife having sex with another man and do nothing. It is frequently the lack of response (including sex) on the part of their SO that pushes the wife over the edge. Often, by the end of the story, the woman does not care who sees her fucking - she just wants dick at any cost.
The ironic thing is that many times the person doing the stealing is the protagonist's neighbor, boss, best friend, brother or even father. Which seems odd, because in Japan they value social harmony above all else. The Japanese crank out a lot of these stories, which leads me to believe this may actually be common in Japanese culture. Either that, or they men secretly daydream about it, perhaps as a subtle form of rebellion against their cultural norms.