Not trying to make any broad sweeping generalizations about Japan, but I have heard that they're not too hung up over what may "turn someone on". If you've got something that turns you on, then, that's your business. Getting all judgmental about what another person seems to react erotically to doesn't seem like a useful way of spending one's time. If enough people are turned on by it, then there's a market for it and for some of those markets people make games like this.

This doesn't make the people playing such a game "rapists" anymore than people playing a first person shooter are "murderers". It's a game, not a clear window into the soul of a nation's quirks.