Shinichi Izumi's life takes a turn when a creature called a Parasyte attempts to infiltrate his body in order to take control of it, but it ends up burrowing into his right hand and both are forced to cooperate.

Shinichi and his Parasyte, now named Migi, battle for control of Shinichi's arm as the number of Mincemeat Murders increases. But when an encounter with another Parasyte turns hostile, they must work together if they hope to survive.

Also known as Symposium. Sinichi and Migi come across two more of Migi's kind - one, a new teacher at Sinichi's school named Ryoko Tamiya, has the ability to keep a low profile and adapt; while the other is an evil creature who will continue to kill humans mercilessly until the day he dies. He sees Migi as a threat to his livelihood that must be taken care of immediately. Written by jenbug1980

While Shinichi and Migi are learning to work together, Shinichi's relationship with his parents (especially his Mother) is becoming more distant and strained.

A violent confrontation with a gang brings Shinichi face-to-face with a girl named Kana, who begins to take an interest in him. Shinichi's parents continue their vacation, but their trip is cut short by an unexpected attack.

With Shinichi at the brink of death, Migi takes drastic actions to ensure his host's survival. After a trying recovery, Shinichi learns that his father is still alive and races to his side before the Parasyte that attacked his mother strikes again.

Shinichi sets out for revenge and runs into an unexpected ally. Together they team up to take down the Parasyte that brutally attacked Shinichi's family. But when Migi falls asleep, Shinichi is forced to engage the enemy on his own.

Life has returned to normal, but Shinichi has not as his ties to Migi continue to change him. As those around him grow wary of this 'new' Shinichi, a Parasyte named Hideo Shimada emerges from the shadows and begins attending Shinichi's school.

The divide between Shinichi and Satomi continues to grow. Shinichi's classmate, Yuko, investigates Hideo and unknowingly stumbles upon a dangerous secret. Meanwhile, Ryoko Tamiya, now known as Reiko Tamura, plots behind the scenes

The confrontation between Yuko and Hideo comes to a gruesome head when Hideo goes on a rampage throughout the school. With Satomi missing, Shinichi must hurry and find her before Hideo can get to her first.

Kana's interest in Shinichi transforms into full-blown obsession when she discovers that she is able to sense his presence. Little does Kana know that it isn't Shinichi she can sense, but something much, much darker.

Migi says that Kana can emit a rather weak signal to other parasites so they can also seek her out. Shinichi tells her the truth while Migi is sleeping but things go unexpectedly.

Shinichi returns to the crime scene to try to keep the feeling of mourning for Kana. He is followed by a human private investigator hired by Ryoko Tamiya and Migi is caught on camera.

The private detective, Kuramori, discovers Shinichi's secret and flees from him. Concerned about Kuramori's intentions, Shinichi seeks help from Mamoru in order to track him down.

Although he still has his doubts, Kuramori reluctantly decides to help Shinichi hunt down Reiko and her group of Parasytes. But when a strange man appears, Shinichi soon goes from the hunter to the hunted.

A powerful Parasyte unlike any Shinichi has ever seen before attacks, and soon Shinichi and Migi are running for their lives. Meanwhile, Kuramori's search for the truth puts his family in harm's way.

After Reiko's judgment is called into question, three members of her own group seek to eliminate her. With Reiko otherwise occupied, Kuramori takes advantage to seek revenge for his family.

With her feelings regarding humanity and the purpose of Parasytes now in question, Reiko encounters Shinichi and Migi one final time. When police arrive on the scene, Shinichi soon finds himself at the center of their attention.

Investigators continue to hold Shinichi, certain that there is something he is hiding. In an effort to uncover his secrets, they soon bring him face-to-face with the serial killer, Uragami, who has a unique ability.

The police commence their operation to take out Hirokawa and the remaining Parasytes. However, plans go awry when the Parasytes attempt to fight back. Things take an even more gruesome turn when Gotou appears on the scene.

In the chaos of the raid, Gotou escapes and vows to return to kill Shinichi. Plagued by fear and with nowhere left to run, Shinichi turns to Satomi for comfort.

Shinichi decides to take Gotou head on, and tracks him to a remote area to fight him. When the battle goes awry, Migi makes an unexpected sacrifice.

With Migi no longer at his side, Shinichi attempts to take on Gotou by himself one final time.

An unexpected but familiar enemy surfaces and Migi gives a final farewell.