Chapter 50

Weapon (狂気, Kyōki) is the 50th chapter of the Parasyte manga series, written and illustrated by Hitoshi Iwaaki.

Overview
''Uragami thinks about his past and what led him to be arrested. As Uragami continues to stare down Shinichi, he comes to the conclusion that he's not a parasite. After leaving, Shinichi talks with Migi about how Reiko may not have been bad, but that there are humans as bad as Uragami. Else where Hirama holds a meeting where they discuss a plan to elimate the parasites.''

Summary
Staring nervously at Uragami, Shinichi internally asks, then denies, if the man might be a parasite. Migi continues sleeping, unaware of his host's distress. The people watching the staring experiment display unease at Uragami's steely stare.

Uragami begins to reminisce on why he can tell apart "monsters and humans"; he had become intimately familiar with human reactions and nature due to the many people he had tortured and killed. He also reveals that he was caught because he had been tailing a parasite and was found with the body's remains.

Hirama watches Shinichi's uncharacteristic nervousness closely, but Uragami tells him that Shinichi probably can't tell parasites apart yet. However, Uragami also had seen something inhuman in the depths of his eyes, then dismissed himself as seeing things. Shinichi simply states that Uragami looks "really scary".

As Shinichi and his father leave for a hotel, Hirama insists they be sent guards for their protection once they get home. Shinichi asks him about Tamura's child. Hirama tells him that the baby will be closely inspected, then, if found normal, will be given up to the proper agencies to be adopted out. He also says Shinichi could claim to be Tamura's relative to have it left with him, but immediately tells him it was a joke.

At the hotel, Migi wakes up. Shinichi talks with him about Uragami the murderer, as well as Reiko Tamura saving him. Migi warns him not to reveal anything to Hirama.

Some time later, Takizawa introduces Yamagishi to Hirama. They have a short discussion about their respective approaches on investigating parasites, and Hirama offers the idea of Uragami being used as a parasite detector when they enter the field. Yamagishi, however, refuses the offer, preferring instead to rely on the scanners he has acquired. This leads to their different thought processes being revealed, with Hirama considering them intelligent enemies and Yamagishi calling their job "pest control".