Project ARMS Vol 4

From the VIZ Media edition

Ryo, Hayato, and Takeshi meet Kei Kurumo, the fourth Arms. Kei turns out to be an agent of an organization called the "Bluemen," and she's out to recruit Ryo and the others to join the Bluemen's fight against Egrigori. However, the Bluemen may turn out to be as insidious and subversive an organization as Egrigori is. All the while, Ryo is losing control of his Arms... or rather his Arms are gaining control of him!

Source: Anime News Network Encyclopedia