The Yata Mirror, Yasakani no Tomoe, and Sword of the Gathering Clouds of Heaven were the Japanese imperial family's Three Sacred Treasures.
"But in fact, there are five of the Three Sacred Treasures."
Uchiha Naruto was, after all, a history student at the University of Tokyo. Moreover, the Uchiha Clan's power system was closely linked to Japanese mythology. He had put considerable effort into this subject and could readily cite the relevant records.
Shinto had a concept called "katashiro," meaning a substitute for a sacred treasure. These were not so-called replicas; rather, through a ritual called "Spirit Transfer," the sacred treasure's divinity was transferred to a substitute, giving it the same standing as the original.
The sacred objects housed in the hundreds of branch shrines of certain major Japanese shrines were katashiro brought over from the main shrine through the Spirit Transfer ritual.
Shinto also claimed that Spirit Transfer did not diminish the original's divinity. Divinity could seemingly undergo mitosis, multiplying endlessly.
It was even more miraculous than Shadow Clones.
The Three Sacred Treasures used historically in imperial accession ceremonies, fought over by various factions, repeatedly subjected to fires, and sunk to the seabed during the Battle of Dan-no-ura were the set kept in the imperial palace: the original Yasakani no Tomoe, a katashiro of the Yata Mirror, and a katashiro of the Sword of the Gathering Clouds of Heaven.
As for the other two sacred treasures, the original Yata Mirror had been enshrined for a thousand years at Kotai Shrine within Ise Grand Shrine in Mie Prefecture, while the original Sword of the Gathering Clouds of Heaven was enshrined at Atsuta Shrine in Nagoya City, Aichi Prefecture.
Even when the Three Sacred Treasures were brought out for an emperor's accession ceremony, they remained inside wooden boxes. Not even the