Shusui

The Shuusui is one of the 21 Ō Wazamono Grade Swords. It was the named blade of the Samurai Ryuuma, who appeared as a zombie on Thriller Bark that had been given Brook's shadow. Roronoa Zoro was given the sword by Ryuuma after the latter's defeat, saying the sword would be satisfied with Zoro as its master. Its blade is black and its hand-guard has flower-like edges.

Abilities
Shuusui is designed to increase the damage potential of the user. At one point, Zoro has commented that Shuusui's greatest attribute is its hardness; saying that even if a dinosaur were to step on it, the blade wouldn't bend. He clearly demonstrated it by blocking Oz's foot with the blade held horizontally. Furthermore, the sheer power of the blade alone was enough to redirect one of Oz's punches.

While it deals a heavy blow and is extremely hard, Shuusui has a few major problems of its own. Just as Sandai Kitetsu turned out to be a "problem child", Zoro describes Shuusui as having a "temper" that makes it harder to wield. Zoro describes Shuusui as quite a bit heavier than Yubashiri, which was extremely light, so it could be anywhere from normal weight to a good deal heavier than normal swords.

While in the hands of Ryuuma, this sword was used by him in both life and death. As a zombie who was imbued with Brook's shadow, Ryuuma has acquired the Fencing Style. Coupled with his already powerful skills, the modifications made to the zombie body, and the powerful attributes of the Shuusui, the Fencing Style has been revamped to the point of being completely different from Brook's original version.

When transferred to the hands of Roronoa Zoro, he used this sword to replace Yubashiri, which had been rusted by Marine Captain Shuu. When first fighting against Oz, Zoro discovered that the Shuusui's weight was the reason it was considered powerful. This was demonstrated by the fact that it created a larger vacuum when the 108 Pound Cannon was performed, and absorbed the vacuums from his two other swords. This weight contributes to the decreased control Zoro has over some of his attacks. As time passed, Zoro began to master over Shuusui's negative attributes.