No connection between that and sex crimes.
http://www.hawaii.edu/PCSS/online_artcls/pornography/prngrphy_rape_jp.htmlDISCUSSION
Within Japan itself, the dramatic increase in available pornography and sexually explicit materials is apparent to even a casual observer. This is concomitant with a general liberalization of restrictions on other sexual outlets as well. Also readily apparent from the information presented is that, over this period of change, sex crimes in every category, from rape to public indecency, sexual offenses from both ends of the criminal spectrum, significantly decreased in incidence.
Most significantly, despite the wide increase in availability of pornography to children, not only was there a decrease in sex crimes with juveniles as victims but the number of juvenile offenders also decreased significantly.
These findings are similar to, but are even more striking than, those reported with the rise of sexually explicit materials in Denmark, Sweden and West Germany. The findings from Europe were, in turn, more dramatic than those reported for the United States. Kutchinsky (1991) studied the situation in Denmark, Sweden, West Germany and the U.S.A. following the legalization or liberalization of the appropriate pornography laws in those countries. The first three countries mentioned, decriminalized the production and distribution of sexually explicit materials in 1969, 1970, and 1973 respectively. In the U.S.A. there was no widespread decriminalization or legalization but, as in Japan, interpretations of the laws seemed to change and prosecution against SEM decreased markedly. Concomitantly, the availability of pornography increased commensurably. Kutchinsky studied the course of sex crimes for the 20 year period 1964 to 1984. Thus his period of study overlaps with the first half of ours.
Kutchinsky found (1991) that in Denmark and Sweden adult rapes increased only modestly and in West Germany not at all. In all three countries, nonviolent sex crimes decreased. The slight increase in Denmark and Sweden, was thought by some most probably due to increased reporting as a result of greater and increasing awareness among women and police of the rape problem (Kutchinsky, 1985b, pp. 323). In Japan too, over the two decades reviewed in the present study, there was also most probably an increasing likelihood of reporting which makes the decrease in sex crimes seen in Japan even more impressive.
Similar to our findings, in Denmark and West Germany the most dramatic categories of sex crime to show a decrease were rapes and other sex crimes against and by juveniles. Between 1972 and 1980 the total number of sex crimes known to the police in the Federal Republic of Germany decreased by 11 percent; during the same period the total number of all crimes reported increased by 50 percent. Sex offenses against minors (those under 14 years of age) had a similarly slight decrease of about 10 percent during this period. For those victims under six years of age, however, the numbers decreased from 1,421 cases in 1972 to 579 in 1980, a decrease of more than 50 percent (Kutchinsky, 1985b; pp. 319).
Other researchers have found similarly. In Denmark homosexual child molestation decreased more than 50 percent from 74 cases in 1966 to 20 cases in 1969 (Ben-Veniste, 1971; pp. 254). These decreases in sex crimes involving children are particularly noteworthy since in Japan, as in Denmark, for the time under review, there were no laws against the personal non-commercial possession or use of depictions of children involved in sexual activities; so-called "childporn" (Kutchinsky, 1985a; pp. 5). Considering the seriousness in how sex crimes against children are viewed in both cultures, this drop in cases reported represents a real reduction in the number of offenses committed rather than a reduced readiness to report such offenses.
Correlated with an increase in pornography we found a decrease in gang rapes in Japan. Again, similar findings had been reported elsewhere. In West Germany, from 1971 to 1987 group rape rates decreased 59% from 577 to 239 cases. In contrast with these findings in Germany where rape by strangers decreased 33% from 2,453 to 1,655 cases (Kutchinsky, 1991 pp. 57), in Japan the number of rapes committed by individuals known to the victim, decreased and rape by strangers increased. Since rapes by strangers or groups are more likely to be reported than date or marital rapes, again there is little doubt these findings in Japan represent real differences. It is also noted that the Japanese police focused more heavily on the control of rape by strangers than on date rape or rape by a known assailant.
Even if porn did lead to sex crimes (which is up for grabs. Some studies find no connection, some find a positive, some a negative correlation), whether we should ban and control it or not is another issue.