As my urban fantasy Shinto novel, Tamao, will be released tomorrow, it should be obvious that I do not think that there is anything wrong, in principle, with Shinto-based fiction. That said, I do have some thoughts.
First, and most importantly, I have already said that no-one has the authority to regulate others’ Shinto practice in general, and that goes double for fiction. Fiction is not even claiming to be real, so an attempt to regulate fiction is to say that you cannot mention certain things even if you are not claiming that they are true of Shinto practice or the kami. This is even more true for fantasy fiction, where it is obvious that you are not claiming that the real world is this way.
As also mentioned before, this also applies to attempts to regulate people who have no claim to be Japanese. They can practise Shinto or write Shinto fiction, and no-one has standing to criticise them for doing that as such. That means that anyone who says to someone “you should not be writing Shinto fiction” is acting wrongly, in my opinion.
That does not mean that Shinto fiction is immune to criticism. Most obviously, if it is aesthetically bad fiction, it can be criticised on those grounds. Ridiculous plots and unconvincing characters are a problem no matter what the topic of the fiction.
Someone may also find a particular piece of Shinto fiction offensive, and say so. This is information that the author may want to take into account, but it may make no difference, and that is fine. I am sure that Philip Pullman knew that some Christians would find the His Dark Materials series offensive. On the other hand, if the author is being accidentally offensive, they may well want to know, and make revisions, and that is also fine. It is, however, entirely up to the author, and the offended person has no further claim against the author. Their recourse is to not re-read the book. (Incidentally, I think it is possible to be offended for reasons that suggest a moral failing in the person offended, rather than the person giving offence. That would be a good reason for the author to do nothing.)
The question of accuracy is a tricky one for fiction, as fiction is made up. This is particularly true for, say, Shinto-inspired secondary world fantasies. The practices in the secondary world will not be, and should not be, exactly the same as in the real world, and therefore differences are not mistakes, but artistic choices. I think the only possible criticisms here are aesthetic. For urban fantasies, for example, it is possible to say that a deviation from actual practice is large enough that it should be a significant part of the plot or background, and that it does not seem to be. The author, and other readers, might disagree, but that is a legitimate aesthetic criticism.
When it comes to my writing, of course, I have my own standards. Tamao is urban fantasy, and the general Shinto background is as accurate as I can make it. It would severely disturb me if the description of the placement of a sanbo had it facing the wrong way, and that was not supposed to make a point about the inexperience of the person making the offering, or something similar. Would any of my readers notice? Probably not, and so if I did want to make the point, I would have to have another character point it out as a mistake. If I write secondary-world fantasies, which is a possibility, then pseudo-Shinto practice is likely to be very similar to Shinto practice, with certain well-defined and significant differences, simply because that would make it easier for me to remember my own setting and avoid continuity errors.
Coming back to urban fantasy, however, I find that I am uncomfortable with having real kami, such as Amaterasu Ōmikami, as characters. Tamao himself is a fictional kami, and while Amaterasu Ōmikami is mentioned, she is not a character. The same applies to having real people as characters. Jinja Honchō is not directly involved in the plot of Tamao, but if I wrote a sequel where it did feature, it would have fictional staff. (Apart from anything else, I would feel really weird about writing myself into the book as a character simply because I actually work at Jinja Honchō, rather than for some tricksy postmodern literary purpose.)
This is not primarily a concern about being sued. (The law on that is unclear, because fiction claims to be untrue, and thus it is hard to show that a fictional portrayal is libellous. It is not impossible, however.) Guy Gavriel Kay, who writes extremely good fantasy fiction in not-quite-the-real-world, has said that he does that, in part, because he is unhappy putting thoughts in the head of actual historical figures, but has no problem doing so with fictional analogues. I have come to sympathise with that position, and it is why Tamao does not include real people.
My position on real kami is, naturally, a little more complex. I am not sure that the kami exist as the sort of thing that can have thoughts or reactions — put simply, the “real kami” may well be fictional. (As I have written about before, it seems that at least one real kami is fictional, which makes this issue even more convoluted.) Even if they are, however, they are not my fiction. There are, further, people who think that the real kami are real and have thoughts and emotions, and they might well be upset by a fictional portrayal of their kami. I know some of these people personally, and I do not want to upset them. (As noted above, I have the moral right to do so — but I am also at liberty not to.) Thus, I am avoiding making real kami central elements of my fiction.
Unlike Kay’s characters, my kami are not analogues of real kami — there is no real kami that matches Tamao. On the other hand, Tamao is supposed to fit naturally within the Shinto worldview as a kami; he does not exist, but it would not be remarkable if he did. That is the general approach I have taken. None of the specific people, jinja, or matsuri that play a significant role in the novel actually exist, but none of them would be remarkable, within Shinto, if they did.
That is my current policy for writing Shinto fiction. It is just my policy, and other people writing Shinto fiction need not follow it. Further, I might change my mind in the future. For now, however, this is where I stand.