Throughout this year, a series of elaborate ceremonies are being held in Japan to mark the enthronement of Emperor Naruhito and the beginning of the new imperial era, named Reiwa, said to mean "beautiful harmony."

The Daijosai, the most secretive and arguably controversial part of those ceremonies, was set to begin Thursday evening and continue into the early hours of Friday. The ceremony is a Shinto rite during which a new emperor prays for peace and a rich harvest for the nation.

The ceremony, which originated centuries ago, is mysterious because the exclusive ritual is attended only by the emperor and a handful of female assistants, all wearing traditional-style dress, and according to Shinto beliefs involves deities descending to the ground during the ceremony.