One of the interesting features of Japanese media, which I have been trying to read in English translation as of late, is the regularity of "groping" stories. With charming titles like "Frisky farmer nabbed for fondling policewoman's breast" (which tells the story of a farmer who approached a plainclothed policewoman from behind and intimately hugged her before running away, and eventually, getting caught), these concise descriptions tend to appear, if not daily, then at least three or four times a week. For more examples see here, here, here, and here.
Groping is actually a very widespread phenomenon in Japan, with 64% of women claiming to have been groped at least once during a recent survey. However, rape generally is much less common, at least compared with other countries. For example, the sexual assault rate of Japan is approximately 1/10 of the sexual assault rate in the United States.
One could try to come up with an institutional explanation for this: Japanese are more likely to use the subway, and subway cars in Japan are more likely to be packed, resulting in a grope-causing atmosphere. But the same argument applies to many other countries (Russia, Italy, much of eastern europe) without such extensive groping-related problems. A cultural explanation seems more likely: it appears there is something about Japanese culture that, while making sexual assault overall fairly uncommon, predisposses the (male) population toward grope-and-runs.