The whole world is about to change one quiet evening with the arrival of parasytes who devour human brains. One of their eggs lands at the home of Izumi Shinichi, a high school student. The hatched parasyte attacks Shinichi, but it faces unexpected resistance and fails to infiltrate his brain.

Shinichi and Migi arrive at the park, only to find Tamura holding her child. As Shinichi struggles to quell his fury at the sight of her, Tamura unleashes a flurry of questions about the meaning of the parasites' existence and what humanity means to them.

Suspecting Shinichi's connection to the parasite cases, Hirama arranges to have Shinichi meet with Uragami, a convict with a peculiar ability. Although cleared of any suspicion and able to return to his high school life, it isn't long before Hirama appears once more before Shinichi. A government operation to neutralize the parasites with Hirokawa is about to begin...

The joint operation by the police and the strike force to eliminate the group of parasites led by Hirokawa has begun. Yamagishi's unit uses their special sensor system to hunt down the parasites. Amidst the chaos, human victory seems all but confirmed. But the tables are about to be turned by a single parasite...

The assault squad succeeds in eliminating Hirokawa, the parasites' leader, but they find themselves in a bind when the ultimate parasite appears. Their failure to eliminate Gotou strikes fear into Shinichi's heart--who will give him the final courage to face Gotou?

With Gotou's defeat, Shinichi's life is finally back to "normal." Though saddened by Migi's sudden departure, Shinichi moves forward with his life. However, a final threat appears...