On the 18th of this month, the Tennō and Kōgō (the Emperor and Empress) visited Jingū at Isë, and paid their respects at the Gekū and Naikū. The purpose of the visit was to inform the kami of the Tennō’s upcoming abdication, on the 30th of this month.
As the main kami of the Naikū, Amaterasu Ōmikami, is, according to myth, the ancestor of the Tennō, important events in the Imperial family are always formally announced to the kami. This includes such things as foreign trips, but for relatively minor things someone is sent on behalf of the Tennō. Only major life events are announced in person. For example, when members of the Imperial family come of age, it seems to be customary for them to visit Jingū to announce that fact, and similarly for marriages of male members of the Imperial family, when the new wife joins the Imperial family. (I think women marrying out, and thus leaving the Imperial family, visit before their marriage to announce that.)
The accession of a new Tennō has previously been reported in person; the current Tennō visited Isë for that purpose in 1990. However, this is the first time that an abdication has been reported in this way. This is because this is the first abdication since the early nineteenth century, and until the Meiji Revolution in 1868, the Tennō never visited Jingū in person. He (or she) sent emissaries on special occasions, and had a permanent representative at the jinja, but never visited in person. There was, presumably, some reason for this, but the books I have read either say “there was, presumably, some reason for this”, or speculate about the status of the Tennō and try to draw conclusions from the form of the matsuri that were performed in the Imperial Palace. Thus, I strongly suspect that nobody actually knows why. It is, structurally, odd, as in the ancient period the head of a family normally performed the matsuri to honour the ancestral kami, and for the Imperial family, that would be the Tennō. In any case, that tradition, like most others at Jingū, was done away with at the Meiji Revolution, and visits by the Tennō now take place every few years.
When the Tennō visits Jingū formally, the sword and the jewel, from the three sacred treasures, travel with him. Historically, the sword and the jewel went everywhere with the Tennō, but that custom was discontinued shortly after the end of World War II. The reasons are not, I believe, entirely clear, but it is generally assumed to be a combination of practical issues, as Shōwa Tennō travelled a lot in the chaotic aftermath of the war, and concerns about provoking the Americans by surrounding the Tennō with religious symbolism. The Shinto establishment was unhappy with this change, and campaigned to have the custom restored. They succeeded in 1974, when Shōwa Tennō visited Jingū after the Shikinen Sengū, although the restoration was limited to visits to Jingū.
The visit was shown on television, and it is easy to see why the custom was not reintroduced more generally. The sword and jewel are both in brocade boxes, so you cannot actually see them, and while the Tennō is riding in a car, one is placed either side of him (looking a lot like how you deal with suitcases when you have too much luggage to fit it all in the boot). When he gets out, each box is carried, slightly above eye level, by an attendant. The sword is carried in front of the Tennō, and the jewel behind. (The boxes are obviously different shapes, and unless the sword is very short and the jewel is very long, it is that way around.)
For a formal visit to Jingū, this is entirely appropriate, and it could even be extended to visits to other jinja. However, it would be completely impractical when the Tennō is, for example, visiting evacuation centres after a natural disaster. This is probably why the Shinto establishment seems to be happy with the current situation, and is not campaigning for the practice to be expanded to cover all Imperial visits.
This visit is intended to be the Tennō’s last visit to Jingū as Tennō, and his last trip outside Tokyo prefecture in that capacity, so it provoked a lot of retrospectives of the Tennō and Kōgō’s visits to places in Japan. Television showed a map of Japan with pins in all the places they had visited, whether before or after the accession (there are a lot of pins), and Jinja Shinpō had three pages dedicated to jinja that they have visited. They have certainly been very dedicated to their job.