Parasyte is a seinenmanga written by Hitoshi Iwaaki, and is particularly famous for its usage of Body Horror.One night, strange spores fall from the sky onto the earth. They spawn out weird little worms that quickly infiltrate human infrastructure, looking for host bodies. The worms crawl or burrow their way into the head of a human host, transforming it and the brain inside. This effectively kills the victim, replacing the host's personality and intellect with that of the Parasite. The Parasites have a ravenous appetite for the flesh of the species they take over - in this case, human flesh.But one specific worm goofs it up - because its intended target, an Ordinary High School Student named Shinichi, was wearing headphones, the parasite can't get to his brain, and instead ends up living in Shinichi's right arm. The little guy is called Migi (Japanese for right), and because of this unique situation, Shinichi and Migi are sharing the same body, but still possess their own individual intellects. This gives them an edge in battling the other Parasites, who see Shinichi's ability to think independently as a threat. Shinichi also feels compelled to fight other Parasites, who kill and eat humans as a source of food, whereas Migi, like other Parasites, is incapable of emotion and only fights to preserve his own life. And so, Shinichi is forced to deal with all kinds of teenage issues while keeping a horrifying secret and having to battle against hordes of other Parasites who want to use him (like Reiko Tamura, a scientist and Shinichi's teacher), kill him (just about everyone else) or worse.Parasyte was first published in North America by Mixx (now better known as Tokyo Pop) where every character was Americanized by changing their names (for example: Reiko Tamura was renamed Tamara Rockford, while Migi was "Lefty" because the pages were reversed); mild censorship of sexual elements (though the gratuitous violence was left untouched); and many cultural differences being waved away. Later, Del Rey got publishing rights to the series and re-released it, reverting the changes Mixx made and using a more accurate translation. A live action film adaptation was apparently in the making, but seems to have been abandoned.
Ax-Crazy: Kabuto. Crosses into Moral Event Horizon and Nausea Fuel territory when he is shown remembering how he got captured, which includes visuals of some of his victims, one of whom he had sex with after he decapitated her.
Betty and Veronica: Shinichi gets into something of a Love Triangle with his current girlfriend, Satomi Murano (Betty), and the rebellious girl Kana (Veronica). Kana unfortunately dies, and because of the missed schooling, his future with Satomi is uncertain at best.
Big "NO!": Shinichi has one when Kabuto is about to cut Satomi's throat, and again when she's falling from a building.
Bittersweet Ending: The Parasites' organization is broken, Goto is dead and the Parasite race is apparently on the decline, but it's come at a heavy price. Because of all the school he missed fighting the Parasites, Shinichi can't get into college, tantamount to a death sentence in modern Japan and thus his future with Satomi is uncertain at best. Migi has put himself into an induced coma for reasons known only to him, Shaba is going senile and it's implied that with the Parasites fading away, humanity will eventually render Earth completely uninhabitable.
Granted, it all depends on the way you view the ending. It can be construed as an Earn Your Happy Ending. Migi decides to absorb himself into Shinichi, apparently because of his implied understanding and curiosity of human life. Though Migi seems like he will be there when Shinichi needs his powers to return, thankfully. Shinichi doesn't pass any college exams, but he and Murano, after saving her life no less than 3 times, are very happy just to be together. Shaba and Uda Mori still coexist peacefully. For a reason never elaborated on, possibly senility as the troper above stated, Shaba's communication seems a little off. Nevertheless, the two remain good friends with Shinichi. The earth seems to carry on like it does, and as of two decades in the future, we haven't reached our carrying capacity yet. Lastly, Shinichi is never shown that he lost his superhuman abilities, especially now that more of Migi has regressed inside of him. We can safely assume that Shinichi won't be academically special, but will proceed along daily life with a girlfriend, some small superhuman abilities and a bright future for them both. Finally, he and Migi can always meet up in their dreams.
Deliver Us from Evil: Reiko is revealed to be pregnant after sleeping with Mr. A, another Parasite-infested human. She originally plans to bear the completely normal human child out of dispassionate scientific curiosity, but soon enough, devotes herself to protect her baby once it's born.
Does This Remind You of Anything?: How did Shinichi prevent Migi from reaching his brain? By tying his earphones' wires into a tourniquet around his own arm. Lampshaded—his parents walk in soon after and ask if he's abusing drugs.
The Dragon: Gotoh to Takeshi Hirokawa. Played straight, as Gotoh isa lotmore dangerous than Hirokawa, and eventually, Dragon Their Feet.
Five Rounds Rapid: Played straight, as most Parasites can ignore bullets. Subverted when it actually works on Reiko, and after the humans start using high-powered shotgun ammunition. Double Subverted when THIS doesn't work on Gotoh.
Gag Penis: After discussing with Shinichi regarding his attraction to Satomi, Migi shapeshifts into a giant erection while the two are at a restaurant.
Shinichi: OH, JESUS!
Gaia's Vengeance: Reiko Tamura and the totally human Takeshi Hirokawa believes the Parasites were created to cull the human population to preserve the earth.
Green Aesop: Actually subverted towards the end. Shinichi comes to the realization that no matter how much humans want to empathize with other creatures and understand nature, at the end of the day they're just humans and can only live as humans, for better or worse.
You can't care about the planet without caring about mankind as well.First panel.
Impostor Exposing Test: The military figures out a way to use an x-ray machine to separate a group of mixed humans and Parasites.
It's Personal: After a Parasite took over Shinichi's mother and came very close to killing him, Shinichi becomes a bit more ruthless in his pursuit.
Averted when he's beaten Gotoh, and the pieces are trying desperately to reunite, probably in vain. He's about to leave him like that, but instead makes it clear that it's Nothing Personal before dispatching him, thereby also nicely averting Once Is Not Enough, because he makes sure that he's dead.
Kill It with Fire: Strangely averted here, as practically everything else gets used - dismemberment, impaling, gunfire from bullets to shotguns, and on one occasion, a rock. Flamethrowers are briefly considered, but rejected. The one time it's used (Shinichi's plan to hit Gotoh with a flaming spear while Migi takes off his head) fails.
Crosses the Line Twice: Shinichi and Migi meet Mori Uda, part of a second human-Parasite pair much like themselves, only this one inhabits the lower half of Mori's face. Mori is depicted as going from The Woobie to the Parasite's personal Butt Monkey from the get-go.
Power Perversion Potential: Averted, Migi's ability to turn Shinichi's hand into a giant penis or mass of writhing tentacles never comes up (as by the time our hero's in a relationship, Migi's asleep for good.
Primal Fear: Shinichi can unconsciously cause people to experience this, especially when he's being threatened.
Product Placement: Unintentional, but the appearance of an undisguised McDonald's in chapter 2 is a fairly rare sighting in manga.
They Look Like Us Now: As time goes on, the Parasytes become more and more human, until finally there's no difference between them and ordinary people.
Tin Man: The Parasites all claim to have no emotions; in truth it's actually more complicated. They seem to lack empathy and are generally cold and expressionless, but seem to have something like bloodlust. As for human emotions, they seem to have some that they may feel in different degrees, but they apparently can (with time) develop complex personalities and emotions, like Tamura protecting her son and Migi valuing Shinichi's friendship and sacrificing selflessly for him. See They Look Like Us Now for the final results.
Took a Level in Badass: After recovering from the stab wound that pierced his heart, Shinichi can run at what looks like more than thirty miles per hour, jump more than twelve feet high without a running start, and has reflexes that allow him to actually dodge and turn aside Parasite attacks, which are faster than the human eye can see. He definitely leveled up.
Unable to Cry: Shinichi finds himself unable to shed any tears after he is turned partly parasite by Migi, even when he is forced to kill his own mother, or when Kana is killed by a parasite. He is finally able to cry again when Tamura's sacrifice for her child reminds him of his own mother.
The interesting thing in the original version is that there are two japanese words for "parasite" that are used in the series. The less common one is used when refering to the creatures, but the common one is used only once - when Tamura refers to Humans themselves as the parasites of planet Earth.