Shusui is one of the 21 Great Grade swords and a "Black Sword/Blade" (黒刀 Kokutō?) that was once wielded by the legendary samurai Ryuma. It is prized as the national treasure of the Wano Country. After his death, the katana was buried with Ryuma, until his grave was robbed by Gecko Moria 23 years ago.
Ryuma appeared as a zombie on Thriller Bark, who had been given Brook's shadow. After his defeat, Ryuma bequeathed the sword to Roronoa Zoro, and said he was satisfied with Zoro as the sword's master. The sword then replaced Zoro's Yubashiri which was destroyed by Marine Captain Shu at Enies Lobby. It was then stolen by Gyukimaru and returned to Ryuma's grave. After that, Zoro agreed to leave Shusui behind to replace it for the offered Enma.
Shusui is a black blade that has as distinct white (reddish-purple in the anime) reverse wave hamon (hardening line) that is of a Kanemoto style and its tsuba (hand-guard) has flower-like edges. It also has no accessories on the hilt, being wrapped with black silk. Kashira, tsuba and kojiri end cap are golden, and the sheath is black, decorated with dark red circles split into even thirds.
In descriptive terms, Shusui is a Hira Zukuri katana with a black blade. Shusui has a solid hilt with a samegawa wrapped around it. The kashira is identical to the kojiri found at the end of the sheath. The crossguard is in the shape of a flower, with the sides being dark gold but the edge is normal gold. There are two half-circle holes on each side of the blade. A saw hamon pattern adorns the sides of this blade in a shining dark magenta while the hamon of the blade is colored purple, though it is equally as dark as the black bo-hi. Shusui has a traditional sheath, but a pattern of circles in their thirds can be found stretching across it.
During the Dressrosa Arc in the manga, Shusui's hamon was changed to red, most likely to match its anime color.
As one of the 21 Great Grade swords, Shusui is one of the finest swords in the world, being a national treasure of Wano and also the signature weapon of the legendary samurai, Ryuma, which became a permanent black blade in his hands. Before acquiring Enma, Zoro believed that Shusui was an extremely important necessity for him in order to attain victory in his crew's upcoming decisive battle against Kaido and the Beast Pirates.
Shusui is designed to increase both the damage potential and destructive power of the user to a tremendous extent, as was first demonstrated when Zoro used Shusui against Oars; after using Hyaku Hachi Pound Ho, it created a larger flying slash attack by absorbing the flying slash of the two other swords (Wado Ichimonji and Sandai Kitetsu), thereby increasing its already great destructive power tremendously.
When used by zombie Ryuma and combined with the fencing style (Gentle Blade) of Brook using his shadow and modifications made to his already strong body, Shusui can create a strong blade version of his fencing style, making it far stronger and destructive than the original. Zoro noted that had his battle with Ryuma continued, Shusui would have broken both Sandai Kitetsu and even Wado Ichimonji, another Great Grade sword.
After receiving Shusui, Zoro commented that its greatest attribute is its durability, claiming that if a dinosaur were to step on it, the blade wouldn't bend a millimeter. He demonstrated it firsthand by deflecting Oars' punch when the blade was wielded horizontally, defending against Neptune's gigantic Trident, and the frenzied assaults of an Energy Steroid overdosed Hyouzou.
Though it is capable of dealing extremely heavy blows, Shusui has some major problems. Among them is that it turned to be a "problem child" like Sandai Kitetsu having what Zoro described as a "temper", making it difficult to wield, as well as being significantly heavier than Yubashiri, which contributes to the decreased control Zoro has over some of his attacks. As time passed, Zoro began to master Shusui's negative attributes.
After training with Dracule Mihawk for two years, Shusui has become Zoro's favored blade and has overcome its negative attributes. In conjuncture with his improved strength and skill, Shusui significantly enhances the power of Zoro's Ittoryuu techniques to a greater extent than what Wado Ichimonji was capable of before his training. As a testament of his mastery over Shusui after the timeskip, Zoro used it to cut a massive galleon ship in half before reuniting with his crew, decapitate an enormous dragon in one slash, and with Sandai Kitetsu and Wado Ichimonji, cleanly sliced apart Pica's mountain-sized golem with immensely powerful flying slash attacks.
The sword originally belonged to Ryuma, and was buried with its original master in Wano Country upon his death, where it was prized as a national treasure. It was said that Shusui was not always a "black blade", and it became one after many battles alongside its master.
Thriller Bark ArcEdit
Ryuma wielded Shusui once again when he was revived as a zombie, and later bequeathed it to Zoro upon his defeat.
Punk Hazard ArcEdit
After he saw it, Kin'emon became determined to challenge Zoro so the sword can be returned to Wano Country. While at a restaurant in Acacia, Shusui was stolen by a dwarf named Wicca. Zoro caught the dwarf and reclaimed his sword.
Wano Country ArcEdit
Due to his possession of the sword, Zoro was accused of being behind a series of attacks and was sentenced to commit seppuku, while a corrupt magistrate took Shusui for himself. Zoro managed to identify the magistrate as the real culprit and struck him down, regaining Shusui.
- In SBS Volume 92, Oda drew Zoro's swords personified as humans. Shusui took the form of a man with a long face and a prominent chin, with neck-length light hair and a thin dark mustache.
- In Chapter 599, Zoro's Shusui was shown with a different sheath strongly resembling that of Trafalgar Law's nodachi, Kikoku. Although Oda did not write anything about it, it could be taken as a mistake as Zoro is then seen holding Shusui with its traditional sheath with no comments about the change. This error is fixed in the anime episode that adapts this scene from the manga.
- In Chapter 937, Gyukimaru states that Shusui "became" a black blade in the hands of Ryuma. In Chapter 955, Tenguyama Hitetsu states that by becoming a black blade, Enma could raise in rank into a Saijo O Wazamono, which means that before becoming a black blade, Shusui could have been a Ryō Wazamono.