Jack: Chapter 3

The kagune runs Ogata through and kills him at once, exposing the culprit as a janitor employed by the school. The boys recognize him, and he gives his name as Tanaka, admitting he has worked there for months while finding it hard to move about freely. His presence suggests ghouls may be hiding within the school itself. Fura, convinced Tanaka is the Lantern who slew his friends, charges in only to be kicked aside by Arima, who reminds him that crude weapons are worthless against a kagune.

When Fura doubts Arima can beat a ghoul, Tanaka praises Arima's agility even as he questions his odds. Arima decides the moment calls for Yukimura 1/3. He flips open his guitar case, and a large capsule inside unfolds into a blade-like weapon. Charging Tanaka, he shears off the ghoul's kagune and explains that Yukimura is a quinque, an anti-ghoul arm forged from kagune, the one material capable of matching a ghoul. He then carves Tanaka clean in half and reveals himself to be a Ghoul Investigator, the reason he carries such a weapon.

Once paramedics remove the corpse, Marude thanks Arima but chides him for running a solo undercover operation without his superiors' approval. Fura praises Arima's courage and skill. It emerges that Arima only enrolled to hunt ghouls and had pulled Fura into the effort; now he intends to leave and investigate elsewhere. Angered that Arima will never lead an ordinary school life, Fura resolves to guard his secret and urges him to stay a while longer and live normally, which Arima accepts. The Lantern, however, is still alive, and its unusual kagune and great strength make the case a difficult one.

The janitor Tanaka is exposed as a ghoul and killed by Arima, who reveals himself as a Ghoul Investigator wielding the quinque Yukimura 1/3. Marude reprimands Arima for the unauthorized operation, and Fura persuades him to remain in school even though the Lantern is still at large.

The third chapter of Tokyo Ghoul: Jack spans forty-two pages with a US release of July 19, 2016. It marks the on-page debut of Arima's quinque Yukimura 1/3. The Lantern is glimpsed only in flashback.