Sword of Kusanagi
The Sword of Kusanagi (草薙の剣 Kusanagi-no-Tsurugi, lit. Grass Cutting Sword) is one of the three legendary Imperial Regalia of Japan, along with the Yata no Kagami and Yasakani no Magatama, otherwise known as the Three Sacred Treasures of Japan. It was originally named Ame-no-Murakumo-no-Tsurugi (天叢雲剣, lit. Sword of the Gathering Clouds of Heaven).
It is currently owned by Rinnosuke Morichika.
In Japanese mythology, the Kusanagi was discovered within the fourth tail of the eight-headed, eight-tailed serpent Yamata-no-Orochi when it was slain by the Shinto god Susanoo-no-Mikoto. He later gifted it to his sister, Amaterasu.
Later, it was given to the future 12th Emperor of Japan, Takeru Yamato, in order to protect him. It came in handy during an ambush when, surrounded by a fire set by a warlord, he discovered the sword could control wind. He then used this wind to engulf the warlord and his men in the flames and emerged victorious. With this, Takeru renamed the sword Kusanagi-no-Tsurugi.
One tale says the sword was lost at sea after being stolen, but was returned safely. In The Tale of the Heike, it is told the sword was lost at sea for good. Today, it is supposedly housed at Atsuta Shrine. However, it is commonly accepted that this sword is likely a replica.
Possession of the Imperial Regalia is traditionally held as proof of the Emperor's divinity and right to Japan's throne.
In the Touhou Project
In Curiosities of Lotus Asia, the sword was found in a pile of junk at Marisa Kirisame's house by Rinnosuke. Unaware of its true worth, she lets Rinnosuke have it in return for repairs made to her Mini-Hakkero. It is described as being made of Hihi'irokane (ヒヒイロカネ, lit. crimson ore), a mythic metal. During a non-stop rain, Rinnosuke temporarily comes to believe that these rains are proof of heaven's approval of his possession of Kusanagi.
In Imperishable Night, Keine Kamishirasawa has the spell card Land Sign "Three Sacred Treasures - Sword", along with spell cards representing the other two Sacred Treasures, Land Sign "Three Sacred Treasures - Orb" and Land Sign "Three Sacred Treasures - Mirror", along with Land Scheme "Three Sacred Treasures - Country".
- Wikipedia entry for Kusanagi