Kujakumaru

Kujakumaru (孔雀丸) was the name of a sword wielded by Guren Ichinose. The Ichinose clan passed it down as a heirloom for generations until it came into Guren's keeping.

Events of 2012
Mahiru cuts the sword in half during their first battle using a black katana, telling him this is the power of a Cursed Gear.

Powers and Abilities
Kujakumaru was a sword that had been sealed with the curses of those who had been beheaded by it. The sword was able to prevent the enemy from absorbing the impact of an explosion created by a talisman Guren put in place on his blade, which was supposed to resist any of the Hīragi Family's curses. Once the seal had been lifted, the enemy will soon become cursed by this weapon, turning their body red. As a result, the curse will eventually destroy the enemy's body, causing it to have their flesh be torn apart and atomize.

Trivia

 * In English Kujaku means peacock.
 * The -maru suffix was traditionally used as a way to protect a young child from bad demons (Oni). The custom was adopted during the Edo period for samurai boys.
 * In this usage, it would most likely mean 'perfect' or 'complete' thus making the English translated name close to: 'Perfect Peacock'.