Kuzuryū

Ryū Kuzu is introduced during The Captain Amagai arc as one of Gyōkaku Kumoi's assassins.

Synopsis
Ryu is part of the assassination squad set to catch Rurichiyo Kasumiōji under Hanza Nukui. He faces against Uryū Ishida, who surprises him by revealing his past as a Quincy. Ishida asks Ryū about his sword, so he reveals that it's a Bakkōtō. He explains that these are different from zanpakutos in that they don’t have a Shikai or Bankai, and they instead convert the user's Spiritual Pressure directly into power.

Uryu begins his attack, so Ryū increases his power with the use of his Bakkōtō Shiragari, allowing him to cover the entire rooftop where they're fighting with a dark mist, and shadows of his figure appear everywhere. Ishida tries to destroy all the shadows, but none of his arrows have any effect. Ryū uses the mist as a cover from which to strike Ishida at vulnerable spots. After having his leg injured, Ishida realizes that his opponent has merged with the mist, and shoots his Seele Schneider into a pentagram shape around the battlefield and activates his technique. Ryū gets caught in the explosion but barely survives.

He was later shown with Kumoi, and reports him about the death of Hanza and his comrades. Kumoi decides he has no more use for him after he failed his mission, and told Makoto Kifune to kill him, revealing that he and Kumoi are in fact allies. This also explains why Shusuke Amagai hired him as 3rd Seat.