First reported by The Wall Street Journal, and later confirmed to Autoblog by Toyota, Emperor Naruhito will be riding in a vehicle that does not exist on U.S. roads. Technically, it doesn't exist anywhere else in the world. According to Toyota, the Japan-only Century luxury flagship sedan was selected to be the new emperor's ride in January 2019. The Japanese government announced the decision in a press release, with some explanation of why it was the top choice. The Century will serve as the base, with several features custom-added, including a convertible roof, the first of its kind.
Based on a rough translation of the release, there were several requirements for the car. First, it must be available domestically, hence the Toyota. It must also be larger in presence than the other cars in a caravan, and it must be designed in a way that the emperor and empress can be easily seen, hence the open top. It must also possess extreme safety and high-level performance, both in power and efficiency. The Century ticks all of these boxes. Unfortunately, there is no other information or photos of the car just yet.
The Century first launched in 1967 as way to honor Toyota founder Sakichi Toyoda's birthday. In 2018, Toyota unveiled the first fully remodeled Century since it had been reworked in 1997. It now runs on a hybrid V8 powertrain, and is listed at 19,600,000 yen, or about $175,000.