|Shadow Hearts: Covenant|
This is one of the three weapons used by Susano-O in the final fight.
One of the Three Treasures. Though none has ever witnessed it, legends say that this royal jewel holds the power of life and death. It holds Ouka's soul.
It's only significance in the fight is its ability to heal a large amount of an ally's hp and to erase any positive status effects on the party. It prioritizes the erasing over the healing, which is a good reason to make it the first target.
The Yasakani no Magatama, is one of the legendary three Imperial Regalia of Japan. Representing the virtue of benevolence, it is presented to the new Emperor during their coronation, and said to be stored in the shrine of the Tokyo Imperial Palace when not in use. It's name means something like, "Jade hook-shaped gem".
In Japanese mythology, goddess of the sun Amaterasu, during a fued with her brother, the god of storms, Susan-O, she hid in a cave, depriving the world of the sun, and plunging it into darkness.
In a bid to rouse her from the cave, the other gods hung a mirror, from a nearby tree, garlanded it with necklace of magatama gems, and made a ruckus, as though in celebration, claiming to have found a replacement light.
Curious, Amaterasu peered from the cave, and caught sight of her dazzling reflection, and moved out towards the mirror. The other gods sealed off the cave entrance, so she wouldn't be able to retreat back to it, and pleaded with her to carry on her duties, which she accepted.
The actual historical existance of this specific gem necklace is unconfirmed - there exists no contemporary pictures or illustrations, and only vague written accounts. Only high-ranking Shinto priests and the Emperor may see the treasure, and only then during the coronation.