The spear used by Izanagi and Izanami to create the world is Amenonuhoko.
In the Kojiki, the divine couple were sent to form land from the primordial ocean. Standing on Ame-no-ukihashi, the “Floating Bridge of Heaven,” they stirred the sea with Amenonuhoko, a jeweled heavenly spear. Brine dripping from its blade formed the island of Onogoroshima, where they later established their home.
Amenonuhoko is not one of Japan’s Three Sacred Treasures. Yata no Kagami is the mirror associated with Amaterasu, while Kusanagi is the sword linked to Susanoo and the imperial regalia. Ama-no-Iwato is the cave where Amaterasu hid, so it is a place rather than a weapon.
The creation story continues with Izanagi and Izanami producing the islands of Japan and numerous kami. Izanami later died after giving birth to the fire deity Kagutsuchi, introducing death into the mythic order.