Wow... sensitive topic. Rare to see such intense discussion in just a few days. I'm adding my own oil to fire:
Preface: (1) I don't support a total ban based on simplistic black/white definable distinction (similar to total ban on "r***" theme in US), (2) I do enjoy some amount of NTR or in general JAV showing behavior that's totally illegal or inappropriate or disgusting in real life. Main argument: some aspect of Japanese sexuality is pretty fucked up, and JAV does a big part in normalize/validate (if not really embrace) it.
One thing to consider is Japanese culture don't see sex in some religious angle (burn in hell!) like the West and Middle East, nor see sex as some super strict moral corruption like China. Japan sees sex as (1) baby-making or (2) pleasure activity (mainly for the man). So a woman perform music or dance for man? Fine! Woman perform blowjob for man? Just as fine! Actually I have long argued that in Japanese culture, anything that doesn't make baby is not sex. That's why top idols make such a big deal about creampie un-banning (解禁 ). In the West, losing virginity (defined as penis insertion in vagina or (in the old days) breaking of hymen) is a "life-changing" event. For Japanese, it's only one of many important events: first kiss, first fuck, first creampie. The real significant one is the first time sex without condom. So creampie unbanning for a high profile idol (e.g. Shoko Takahashi) is like public viewing her losing virginity (despite fans-in-the-know already know it's fake semen) :
Flip around, any sex act with condom or ejaculation outside of vagina is no big deal, even if it's r*** and/or incest.
The argument crime rate in Japan is super low is also BS. It's true public security in tourist/rich districts are excellent/world class. But social studies conducted by Japanese researchers (only partially translated into English) reported over the years, that a vast majority of young girls or women had suffered what in the West would be classified as sexual assault. A girl or woman who's been r***ing, over 50% of them would not report a (officially statistic-counted) crime. They go home and take a shower, and cry under a pillow, quietly so as not to alarm their family. Even if there's DNA left behind, mostly she would not kept a sample and have police trace down the criminal. The realistic chance to see the criminal get a reasonable sentencing is pretty terrible, and the chance that she would suffer much much more pain and humiliation at the police station, hospital, court, on newspaper etc etc, the math doesn't work for her.
The argument the industry is just passively reflecting the customer base's desires, is just plain wrong. Of course the industry is profit seeking and must respect the customer demands, but the industry has a huge role to influence the fan taste too. They got the fandom to accept mosaic, don't forget that.
One example, I admit it's totally impractical in legal or regulatory terms, is ban all "meaningless" incest. There are many vids, probably including the Aki Sasaki above is "meaningless" in the sense that the whole vid is almost exactly the same, if the cover doesn't say "incest" in big font. A man and a woman in the same house have sex, they could be husband and wife, boyfriend/girlfriend, neighbors, housewife and pizza-delivery guy, or... if the cover says so, they could be mother/son, father/daughter, brother/sister. The whole vid is almost exactly the same except maybe for the 20 seconds foreplay conversation they address each other. It's totally SILLY!
Some of you maybe old enough to have seen Caligula starring Peter O'Toole and Helen Mirren, Caligula incest with his sister. That's epic cinema. At the same time disgusting and arousing.
My pet theory is not that the fandom actually wish to fuck his mother/sister/daughter. I think there are a lot of otaku who are afraid to talk and flirt and hook up with opposite sex. They only have enough courage to interact with family members, so by extension intercourse with family members. DISGUSTING! Hmmm nevermind, it's a foreign country, why do I care woman suck her son's sperm behind closed door? But it's VERY LAME!
Like I said, it's not practical to define a boundary and ban it. Just because an action is wrong it should not be banned as entertainment topic. Like it's fine to show murder on film, but it should be presented with moral bias. Like Ernst Blofeld can murder, but the film use the murder to tell us Blofeld is a bad guy. 007 has license to kill, but he uses it rarely and only in service to Her Majesty. Esp. he never uses his license to kill as a license to fuck.
Used to be some JAV has a pre-credit screen warning the scenes you will see is wrong and illegal. That should be used a lot more often. Fine if you must masturbate to imaginary sister, but you ought to be ashamed of yourself! Also I think every "real" r*** (not typical NTR, and how to distinguish r*** from NTR, my gods that's another barrel of worm) could be concluded with some punishment scene the r**ist has his penis cut off, with a dull knife.