And all my books are upstairs in the attic, but let’s see how close I can get.
The divinity of the Imperial line of Japan descends via their ancestor, Jimmu Tenno, the first (semi-mythical) Emperor of Japan. He was the grandson of Amaterasu-no-Mikoto, the Sun Goddess and came to power around 660-600 BCE, during the Jomon period.
The divinity of the Emperor was certainly played up during the war by the expansonistic and rabidly xenophobic military sects. Their attempts to purge Shinto of any aspect of foreign influence went very deep, but the actual divinity of the Emperor was much less than what Wester tradition would view as a diety. At most, the prayers directed to the Emperor were intercessory in nature, not an attempt for him to use a supernatural power to directly effect the physical world.
[minor digression]
The Imperial Treasures, as mentioned, consist of the Mirror, the Jewel and the Sword. The Mirror comes from the time that Amaterasu was teased and taunted by Susanos, God of Oceans and Storms. She shut herself up in a cave, plunging the earth into darkness. The other gods/goddesses hung a mirror on a tree branch outside the cave opening and lured her her towards the opening with what can only be described as a burlesque show. When she saw the glow of her reflection in the mirror, she came (or was dragged) out into the open. Susanos was tortured and banished, falling to earth. He found a serpent and killed it, heroically saving a maiden in distress in the process. While cutting out the tail, he found a beautiful sword, Kusanagi No Tsurugi which means “grass parting two-edged straight blade”. The sword was given as a gift to Amaterasu.
I believe that one of Amaterasu’s descendents is given two precious jewels in an underwater adventure, which completes the acquisition of the Imperial Treasures.
The Treasures were placed in the safe-keeping of Jimmu-Tenno as the symbols of his office. Traditionally, the mirror is in the Ise Shrine of Amaterasu, the jewels are in the Imperial Household of the Palace in Tokyo, and the sword is resides at the Atsuta Shrine at Nagoya.
As to where the sword actually is now, that’s a little more of a mystery. The last time it was actually seen was in 1168 AD, at the time of the Battle of Dan-no-Ura, the last battle during the Heike wars between the Tiara and the Minamoto. The Tiara Emperor Antoku drowned, taking the sword with him. The Emperor Sujin did have replicas of the Mirror and Sword made sometime during his reign. The descendents of the Tiara claimed that since the original went down with the Emperor, all subsequent Emperors have been enthroned improperly. The Minamoto argued that the original was still in the Atsuta Shrine adn that the duplicate went down. Although supported by the following Emperors, they were completely dominated by the Minamoto clan and had no actual freedom of decision. Most historians feel that it was the original that went down and the duplicate remains in Shrine.
[/minor digression]
Okay, okay, so it was a major digression.