Hangyaku

Hangyaku (黒刀, Literally meaning: Treason) is one of the one hundred Black Swords that is in the shape of a tantō and was most recently in Kotarō Shimura's possession. Like the other Black Swords, Hangyaku is made of a metal stronger than steel and possess a dark, non-reflective surface and is incredibly sharp. Hangyaku is around 20 cm long and is double edged. The sword possessed no crossguard with the bottom length of the blade (being the widest part) acting as an improvised one instead.

Trivia

 * Out of all of the Black Swords in existence, Hangyaku has had the most owners, all of whom have been killed for the blade. For this reason, Hangyaku is considered cursed.