Shūkurō Tsukishima

is a mysterious individual who is capable of using Fullbring, and the former leader of Xcution.

Appearance
Tsukishima is a tall young man with long dark hair. He wears a long-sleeved collared shirt with suspenders and dark pants. He has a scar across his left eye.

Personality
As a person, Tsukishima appears to be cold, calm and collected in most things he does. He cuts down Uryū without much expression or effort and coolly admits to doing so without any hint of remorse. He also possesses some level of intelligence as he was able to organize and form a group while devising a plan to rid them of their powers.

History
Some time ago, Tsukishima gathered people with Fullbring abilities together, in order to find a way for them to erase their powers. He formulated the plan to pass their powers on to a Shinigami Representative, forming the group, Xcution. However, once this process began, he had a change of heart and used his abilities to kill the Shinigami and those who had been relieved of their powers. Xcution's new leader, Kūgo Ginjō, has theorized that Tsukishima's new goal is to keep Ichigo Kurosaki away from them.

The Lost Substitute Shinigami arc
While Uryū Ishida is waiting outside of Ichigo Kurosaki's house, he spots Tsukishima standing on a nearby rooftop. Tsukishima leaves, causing Uryū to follow him. Using his speed, Tsukishima is able to catch Uryū off-guard and wound his right shoulder.

Sometime after his attack on Uryū, Tsukishima sends Moe Shishigawara to attack Orihime Inoue, but says that he does not need to do anything, because he believes that Shishigawara will not harm girls. As Shishigawara is about to fight Orihime, Tsukishima arrives and tells Orihime that he was the one who attacked Uryū.

Tsukishima introduces himself to Orihime, but Shishigawara interrupts their conversation, insisting that he will be able to take care of Orihime for him and tries to fight her. Tsukishima tells him to go home, but Shishigawara refuses. Tsukishima closes his book and reminds Shishigawara that he told him that he didn't need to do anything, and asks why he is still there. Shishigawara tells him that he wants to be useful to him. Tsukishima then casually remarks that he lost his page and takes out his bookmark, turning it into a sword. He asks Shishigawara if he minds taking responsibility for his lost page. Upon seeing the sword, Orihime asks him if it is a Zanpakutō. Tsukishima replies that it is not; it is actually his Fullbring, Book of the End. He tells Orihime that she can relax, as he does not plan to harm her at this time; instead, he is going to punish Shishigawara, who cannot follow his orders. Orihime moves herself in front of Shishigawara, which causes Tsukishima to remark that she is good-natured to the point where she does not like seeing even an enemy hurt. Orihime denies that being the reason; she informs him that since he attacked Uryū, she cannot let him leave. He merely replies that her reasoning is boring before turning away from her. When Orihime goes to use her powers, he attacks her from behind and appears to seriously wound her, however, she is shown without any damage moments later.

Moe sneezes on Tsukishima while he is eating a meal, prompting Tsukishima to pin him to the table with a fork and ask if he may continue speaking. He goes on to say that Moe no longer needs to do anything regarding Orihime and insists that he stop calling himself a henchman. Though Moe protests, Tsukishima says they already have her and there is no need of further contact. He then wonders whether to attack Sado or Ichigo next, asking what Kūgo would say if he were to meddle with Ichigo directly.

Powers & Abilities
Enhanced Speed: Tsukishima has remarkable speed; as noted by Uryū, his speed is far above that of a normal Human. Tsukishima is fast enough to attack the likes of Uryū and Orihime before they can even react.

Fullbring

 * Tsukishima's Fullbring manifests itself in his bookmark, which he can transform into a katana that has a bookmark-shaped tsuba. Ginjo remarks that to the best of his knowledge, "Book of the End" is a sword with high attack capability that can literally cut through everything.