The accession of the next Tennō is getting very close; it will happen at the end of this month and the beginning of next. Given the importance of the Tennō to the Shinto establishment, at least, it should come as no surprise that they are putting a lot of effort into preparing for the event, and ensuring, as far as they can, that it is celebrated appropriately.
There are a lot of ceremonies associated with the succession, and while they start on April 30th, some of the most important ones, and those most closely connected with Shinto, do not take place until November. The most important of these is the Daijōsai, and the Shinto establishment is currently very exercised by a proposal to roof the main halls for that with boards, rather than the traditional thatch.
As part of their preparations for the ceremonies, Jinja Honchō prepared a booklet describing the main events, illustrated with photographs from the ceremonies performed for the accession of the current Tennō. One of the jobs I have done for them is translating that booklet into English, and they have now put the content online, so that you can read it. As I have mentioned before, this is a translation of Jinja Honchō’s text, and does not necessarily reflect my position on everything mentioned. (However, as it is primarily descriptive, I do not actually have any substantive disagreements: these are the ceremonies that are likely to happen, unless something truly catastrophic happens in the next few months.)
Of the ceremonies that happen around the succession itself, the most significant from a Shinto perspective is the passing on of the sword and jewel. These are two of the three sacred treasures that Amaterasu Ōmikami gave to her grandson, Ninigi no Mikoto, before he descended to earth. The sword is a copy; the original is enshrined in Atsuta Jingū in Nagoya, and has been for well over a thousand years. Spiritually, the copy is equivalent to the original, but nobody is claiming that the actual physical sword used in the ceremony was handed over, in the heavens, by Amaterasu Ōmikami.
The jewel, however, is supposed to be the original.
Both of these items are contained within boxes, like the goshintai at jinja, so the sword and jewel themselves are never, to the best of my knowledge, visible. Thus, officially nobody knows what they look like, and anyone who does know is going to avoid talking.
The sword is what it claims to be. It is a copy of the sword held in Atsuta Jingū, in a religious sense. It may not look similar, but it has the same spiritual significance.
The jewel is different. I have to say that I do not think that the evidence that this physical object was handed over by Amaterasu Ōmikami to her grandson, carried down from the heavens, and then preserved for thousands of years, is really convincing. I could be persuaded that it had been handed down as a sacred symbol of the Imperial office for about 1800 years, because that would not require anything particularly out of the ordinary to have happened. If you reduce the time span to 1300 years or so, I would say it’s actually quite likely, because I am not aware of any stories of the jewel being lost. (Earlier copies of the sword, by contrast, have been.) There is certainly no strong reason to disbelieve. But that, of course, is not the official line.
One of the effects of Shinto not caring that much about belief is that I do not really have any idea how many, if any, priests believe that the jewel was literally given to Ninigi no Mikoto, as described in the myths. Its symbolic importance and place in the ceremonies is unchanged in any case, so with Shinto’s practical emphasis, maybe it does not matter all that much.