Due to the legendary status of these items, their locations are not confirmed, but it is commonly thought that the sword is located at the Atsuta Shrine in Nagoya, the jewel is located at the Three Palace Sanctuaries in Kōkyo (the Imperial Palace in Tokyo), and the mirror is located at the Ise Grand Shrine in Mie Prefecture.
Since 690, the presentation of these items to the Emperor by the priests at the shrine has been a central element of the enthronement ceremony. This ceremony is not public, and these items are by tradition seen only by the Emperor and certain priests. Because of this, no known photographs or drawings exist. Two of the three treasures (the jewel and the sword, as well as the Privy Seal and State Seal) were last seen during the accession and enthronement of Emperor Akihito in 1989 and 1993, but were shrouded in packages.
According to legend, these treasures were brought to earth by Ninigi-no-Mikoto, legendary ancestor of the Japanese imperial line, when his grandmother, the sun goddess Amaterasu, sent him to pacify Japan. These treasures were eventually said to be passed down to Emperor Jimmu, who was the first Emperor of Japan and was also Ninigi's great-grandson. Traditionally, they were a symbol of the emperor's divinity as a descendant of Amaterasu, confirming his legitimacy as paramount ruler of Japan. When Amaterasu hid in a cave from her brother Susanoo-no-Mikoto, thus plunging the world in darkness, the goddess Ame-no-Uzume-no-Mikoto hung the mirror and jewels outside the cave and lured her out of the cave, at which point she saw her own reflection and was startled enough that the gods could pull her out of the cave. Susanoo later presented the sword Kusanagi to Amaterasu as a token of apology; he had obtained it from the body of an eight-headed serpent, Yamata no Orochi.
At the conclusion of the Genpei War in 1185, the eight year-old Emperor Antoku and the Regalia were under the control of the Taira clan. They were present when the Taira were defeated by the rival Minamoto clan at the Battle of Dan-no-ura, which was fought on boats in the shallow Kanmon Straits. The child-emperor's grandmother threw herself, the boy, the sword and the jewel into the sea to avoid capture. The mirror was recovered, but according to the main account of the battle, a Minamato soldier who tried to force open the box containing it was struck blind. The jewel was recovered shortly afterwards by divers, but the sword was lost. There are a number of medieval texts relating to the loss of the sword, which variously contended that a replica was forged afterwards, or that the lost sword itself was a replica or the sword was returned to land by supernatural forces.
The possession by the Southern Dynasty of the Imperial Regalia during the Nanboku-chō period in the 14th century has led modern chroniclers to define it as the legitimate dynasty for purposes of regnal names and genealogy.
The importance of the Imperial Regalia to Japan is also evident from the declarations made by Emperor Hirohito to Kōichi Kido on 25 and 31 July 1945 at the end of World War II, when he ordered the Lord Keeper of the Privy Seal of Japan to protect them "at all costs"