Imperial Regalia of Japan

The Three Sacred Treasures are the imperial regalia of Japan and consist of the sword Kusanagi, the mirror Yata no Kagami, and the jewel Yasakani no Magatama. They represent the three primary virtues: valor (the sword), wisdom (the mirror), and benevolence (the jewel).

The sword Kusanagi was said to have been carved from the tail of the dread serpent Yamato no Orochi, a beast who had been devouring maidens in his valley for generations. Susano'o, the god of storms, came by the family whose daughters had been devoured by the monster and, being having been promised the last daughter's hand in marriage should he triumph, went out to slay Orochi. He proved successful by intoxicating it with a potent sake and decapitating each of its eight heads. As he made his way along the body of Orochi he discovered the blade hidden inside its fourth tail. He dubbed the blade "Ame-no-Murakumo-no-Tsurugi".

Yata no Kagami and Yasakani no Magatama both originate from the legend of Amaterasu and her isolation from the world after her brother, Susano'o, angered her. Susano'o was said to have insulted Amaterasu, claiming she had no power over the higher realms. When Izanagi, their father, ordered him to leave Heaven, he went to bid his sister goodbye. Amaterasu was suspicious, but when Susano'o proposed a challenge to prove his sincerity, she accepted. Each of them took an object belonging to the other and from it birthed deities. Amaterasu birthed three female deities from Susano'o's sword Kusanagi while he birthed five male deities from her magatama. Claiming the gods were hers because they were born of her necklace, and the goddesses were his, she decided that she had won the challenge, as his item produced women.

After Susano'o's defeat he went on a rampage destroying much of the heavenly and earthly realm, including Amaterasu's rice fields; he also hurled a flayed pony at her loom, and killed one of her beloved attendants in a fit of rage. Amaterasu, who was in fury and grief, hid inside the Ama-no-Iwato ("heavenly rock cave"), plunging the earth into darkness and chaos.

Seeing the world die without the sun, the other Kami gathered and plotted to draw Ameterasu from her isolation. The deity Ishikoridome crafted the finest mirror, Yata no Kagami, and hung it on a nearby tree along with Amaterasu's Yasakani no Magatama. Then the goddess Ame-no-Uzume performed a promiscuous dance, causing the other Kami to cheer and make noise.

Intrigued by the commotion, Amaterasu emerged from her cave and immediately noticed her reflection in the mirror. Seeing her own face for the first time, she was captivated by her own beauty and radiance. While she stared at herself, Susano'o placed a large boulder over the entrace to her cave so she could not retreat back inside. Forced to confront her actions and the world she had hidden herself from, Amaterasu promised to return to her duties as the sun that warmed the earth. As a form of reconciliation, Susano'o gifted his sword to Amaterasu.

Many generations later it was bestowed to a warrior named Yamato Takeru by his aunt, a shrine maiden of the Ise Shrine where the sword had been kept. During a battle against a warlord in a grassy field, Takeru discovered that the sword had a mastery over the wind and used this to push back the flames that his opponent had tried to surround him with. Here the blade became known as Kusanagi-no-Tsurugi, the Grasscutter Sword. The blade would, over more generations, end up in the Imperial Palace. it would be moved to Atsuta Shrine in 688 AD, the first definite historical record of its existence.

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.

History with the Warehouse
The Sacred Treasures first made themselves known in 1064 AD, during the reign of Warehouse 6. While records are sparse from the time, it can be inferred that the treasures simply appeared one day in the Religious Section. The artifacts displayed no apparent effects and were mostly left alone until some time later when they just as mysteriously vanished.

This phenomena would recur every few decades for a maximum of three years and minimum of a few days. It was not until late in Warehouse 10's tenure that the legends of the Imperial Treasures came to the attention of the Regents. The next time they appeared in 1614, attempts were made to contain them. All measures proved ineffective, however, when they again vanished in 1615. They would not be seen again until 1904 when they showed up in Warehouse 12.

During this time it was proposed that the artifacts were exhibiting a form of self-preservation, transporting themselves to the Warehouse whenever their home country was under direct threat. Sanctions were made, allowing a special spot or the artifacts to rest should they need to, and rules were put in place prohibiting the attempted interference of their free movement.

The artifact were last seen in 1945, correlating to the detonation o several atomic class bombs in the country.