- Complete Monster: Kabuto is a human being who manages to be many times worse than the man-eating parasites of the story. A sadistic Serial Killer, he considers other people his "playthings" and gets off on all acts of cruelty he can inflict them, including murder, rape, mutilation and cannibalism. After he was caught and forced to work for the army, he gleefully helped them slaughter dozens of parasites along with a few innocents before killing the police officer escorting him and escaping. Knowing that it was only a matter of time before being caught again, he decides to spend his last days as a free man forcing protagonist Shinichi, who had never done anything to him, to confront him. He does this by killing more innocents, capturing Shinichi's girlfriend Murano and threatening to "have a lot of fun breaking this little doll" if he doesn't comply, only to throw her from a rooftop and stabs Shinichi when he does. A depraved fiend, Kabuto was even able to see through the parasites' disguise because he was, like them, a monster hiding behind a human appearance.
- HSQ: Parasyte could easily be renamed to "HSQ: The Manga".
- Narm: When Shinichi is at death's door, Migi fills the roles of trauma surgeon, nurse, AND organ donor in order to save his life. It should have been the dramatic turning point of the story in more ways than one, but thanks to the visuals that accompany this scene... not so much.
- Squick: see Fan Disservice in the main page.
- Tearjerker: A lot of these.
- The deaths of Kana and Shinichi's mother.
- Migi going into a self-induced coma of sorts.
- Ugly Cute: Migi when in 'talking' form.
- Uncanny Valley: In the story, Parasites generally are indistinguishable from normal humans. However, they tend to have completely blank expressions due to not having emotions, and the artwork often gives them slightly overlarge and sharply-defined eyes that give them a sinister appearance. Extremely twisted humans, such as Kabuto and Takeshi Hirokawa, also have these eyes. There's also Sanji.