A

A (A, Ē) is a Parasite who considers Shinichi a threat. Ryoko calls him a fool, while Migi describes him as "not one of our smart ones". He is a minor antagonist early in the series.

Appearance
In his first appearance, A wore glasses and had short brown hair and wore a business suit. After a confrontation with some thugs, he altered his face. He then went with longer brown hair, a sharper, rougher looking face, and dead eyes. He was often seen wearing a brown jacket.

Personality
A is very violent and unstable even by the standards of his species. While most Parasites at least try to blend in with society, and some can even be reasoned with, A thinks only about eating humans and never even bothered to learn his host's name. He is shown to be paranoid and acting mostly on instinct instead of reason, attacking Shinichi's school in broad daylight to try to kill him simply because he might pose a threat.

A has been described by his fellow parasites Ryoko Tamura (then Ryoko Tamiya) and Migi as reckless and not very smart, which is supported by his aforementioned decision to attack Shinichi's school, as well as his grave underestimation of Shinichi's abilities. However, he is shown to not be a complete idiot, as he is able to correctly guess that Shinichi had put up a barrier to protect himself and get to him through the window from the floor right below, hereby trapping Shinichi in one place with the Parasite.

Plot
In the anime he is first seen "rescuing" a young woman from a group of men. After knocking the men out, he starts escorting the woman home. He is then attacked with a metal pipe by the same men he previously beat. Shocking the attackers by being unfazed, he then states that his stomach wouldn't be large enough to hold four people, revealing himself as a parasite. He forms his head into multiple blades and kills the men, which causes the woman to start screaming, then quickly decapitates her. After witnessing the mess he caused, he decides to change his appearance just to be safe. (In the manga the character who did so seems to be a different parasite as he has a personality unlike A's.)

In the manga he is seen approaching a lion that had escaped from the zoo, noting that a creature like that shouldn't be in this part of the world. Realizing that the animal fears him, he prepares to leave. Due to the lion's ignorance towards its instincts, it tries to attack him. A quickly changes his head into multiple blades and splatters the beast's head apart. Grabbing a towel, he cleans himself off and makes his leave. Onlookers, shocked at what they've just witnessed, come to the conclusion that he had an explosive on him.

He then participated in Ryoko's experiment and impregnated Ryoko's host body with a normal human baby. After Shinichi found out Ryoko was a parasite, Ryoko invited Shinichi and Migi to meet A and her to exchange information. A thinks that Shinichi is a threat because of the failure of Migi to obtain Shinichi's brain. He decided to kill Shinichi while he was still at school. A encountered and killed some teachers and staff, when they attempted to stop him from entering the school.

After making his way through the school, he senses Shinichi is on the floor above his and crashes through a window to get to his location. Noting that Shinichi has created a barricade, A says that he's only blocked off his escape routes. As they begin fighting, A pays no mind to Shinichi, only worrying about Migi. This neglection caused him to be stabbed in the stomach by a desk leg, causing him great confusion. Managing to escape from them, partially due to Shinichi's refusal to kill him, he tries to find Ryoko and merge with her host. Instead he is ultimately killed by an explosion caused by Ryoko.

The police were never able to find out his true identity, as most of his upper body was destroyed in the explosion.

Abilities & Powers
Being a parasite, A can shapeshift from the head up and and harden his cells for offensive or defensive purposes, as well as detect other parasite signals and automatically emit his own. He can also maximize the host body's physical potential and disregard pain.

In the manga he was shown to have enough strength where when he punched a wall it cracked, but his arm broke in the process. He is one of the few parasites to use his tentacles to move his human body around, as shown when he used them to propel himself through a window.

Weaknesses
Like all parasites, A requires a host body with functioning organs to survive, and would die if he were separated from the body or it was destroyed. Fire can cause his parasite cells to "freak out", making him lose control. He is also susceptible to poisons or caustic chemicals, which would either kill parasite cells on contact or make his host body fail. He used his host body roughly, causing him to break an arm when he struck out with all of his host body's strength and hit a wall.

He believed humans beneath notice, and this ignorance towards the human species allowed Shinichi to get an easy hit on him. He also believed that because he could change his face, he would suffer no consequences from attacking in broad daylight, which was proven wrong when Ryoko decided to act against him.

Trivia

 * In the movie Parasyte: Part 1, he kills Nobuko Izumi and takes over her body.

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