In Japanese mythology, the sacred sword Kusanagi is discovered inside Yamata no Orochi’s tail.
After Susanoo cuts through the serpent’s tails, his sword strikes something hard inside the fourth tail. He discovers a remarkable blade and sends it to Amaterasu as a gift. In the Kojiki, it is called Ame-no-Murakumo-no-Tsurugi, meaning Sword of the Gathering Clouds of Heaven; the name Kusanagi becomes prominent later.
Kusanagi is traditionally counted among the Three Imperial Regalia of Japan, alongside the sacred mirror Yata no Kagami and the jewel Yasakani no Magatama. The regalia symbolize imperial legitimacy.
The sword’s physical whereabouts are not publicly verified, and the sword kept at Atsuta Shrine is traditionally regarded as Kusanagi. Thus, the mythological identification and the historically inspectable object should not be treated as identical evidence.