Split Soul Katana

The Split Soul Katana is a cursed tool used by Toji Fushiguro and Maki Zenin later wielded a replica created by Mai Zenin. It's a blade that can bypass physical toughness in order to split the soul, but this power can only be exerted by someone who can observe even the souls of even inanimate objects.

Description
As its name implies, the Split Soul Katana ignores any physical resistance to cut into the soul of its target. Full use of its power requires a user with eyes that can perceive souls of organic and inorganic matter. Only people who have broken away from cursed energy and possess heavenly restricted bodies of steel like Toji Fushiguro and Maki Zenin can truly wield it.

Toji Fushiguro
Toji used the Split Soul Katana frequently on his mission to assassinate the Star Plasma Vessel, Riko Amanai. After it appeared as if he was swallowed by one of Suguru Geto's curses, Toji ripped the massive worm-like creature apart from the inside using the blade. He also used the blade to slice clean through the Rainbow Dragon, the cursed spirit with the hardest skin in Geto's arsenal at the time.

Maki Zenin
When Mai sacrificed her life, she left behind an exact replica of Toji's Split Soul Katana. It serves as Maki's last connection to her sister and the weapon she wielded to enact her promise to destroy everything. Maki destroyed the entire Zenin clan using the Split Soul Katana, starting by bisecting her father's head with a single stroke of the blade. Dual-wielding it alongside the Dragon-Bone, Maki annihilated the Kukuru Unit by slashing numerous men apart with a sword in each hand. She finished her rampage through the Hei by using the Split Soul Katana to sever Jinichi Zenin's head from his body. When Maki used the replica to eliminate the leftover members who were absent during her attack, only trace amounts of the cursed tool's cursed energy were left behind.