A katana forged by Masamune, a swordsmith from Sagami.
It is unclear when the deep scratches on the blade were made, but their location on the ridge and back — facing the wielder — has sparked speculation that they were made when Ishida Mitsunari's Guardian Spirit Izuna raged against being compelled into inhabiting the sword.
In 1600, when Mitsunari was sent to be confined to Sawayama Castle, Tokugawa Ieyasu assigned his son Yuki Hideyasu to serve as guard on the journey from Osaka to Sawayama. Mitsunari gave a Masamune sword to Hideyasu in gratitude, and that sword too had the scratches on its blade. For the rest of his life, that katana was Hideyasu's favourite.