Kusanagi-no-Tsurugi

Origin
One of the three sacred treasures of Japan, the mirror was passed down from the sun goddess Amaterasu to her descendants Ninigi and later Emperor Jimmu. After Amaterasu was tricked to return to her duties, her brother Susanoo gave her a sword as an apology for his behavior. Originally called Ama-no-Murakumo-no-Tsurugi ("Sword of the Gathering Clouds of Heaven"), Susanoo discovered it inside a tail of the eight-headed serpent Koshi, which he slayed to stop its reign of hunger.

Many generations later, a warrior loyal to the emperor known as Yamato Taker was entrusted with the weapon. He found himself trapped in a flaming field surrounded by the enemy’s hordes. While attempting to cut a viable path through the grass, he discovered the blade could create wind in whichever direction he cut. Taker fanned the flames upon his enemy and narrowly escaped from certain death, renaming the relic Kusanagi-no-Tsurugi ("Grasscutter Sword") in honor of his miraculous escape. However, Taker fell in a latter battle when he attempted to battle a monster without the Kusanagi in hand.

Said to represent valor, the sword is one-third of the Imperial Regalia of Japan. Allegedly kept in Atsuta Shrine, its existence cannot be confirmed as access is consistently denied. At some point in the twelfth century the sword was lost, although it somehow returned to the royalty by supernatural means.

Effects
Releases wind currents in whichever direction it slices. The size and strength grows in respect to the level of control the wielder holds. It also increases the sketchiness of ordinary situations, increasing the risk factor of events going horribly awry.