Bakuzan

The Secret Sword Bakuzan (秘剣縛斬) is a special sword used by Satsuki Kiryūin with the ability to cut Life Fibers. It was split into Bakuzan Gako and Bakuzan Kōryu after Satsuki was defeated by Ragyō Kiryūin.

Secret Sword Bakuzan
Satsuki Kiryūin owns Secret Sword Bakuzan, a black bladed katana. It is very powerful, able to fight evenly with the Scissor Blade.

Bakuzan Gako
The Bakuzan Gako is a small dagger wielded by Nonon Jakuzure. She gives it back to Satsuki after rescuing her.

Bakuzan Kōryu
The Bakuzan Kōryu is larger than the Bakuzan Gako, having been reforged as a short sword. It is wielded by Ira Gamagōri at first, and is later given to Uzu Sanageyama. As Gamagōri states, it is "more [his] thing". Sanageyama gives it back to Satsuki after she was rescued.

Trivia

 * Satsuki's big toe's toenails are made of the same material as the Bakuzan.