Seongbin Yu might as well be one of Carnby Kim's most divisive characters. Seongbin is completely hated by a significant share of the fandom due to being a murderousJerkass with few sympathetic traits and his bullying of Gyuhwan and other characters, among other horrible actions. Meanwhile, another large share of the fans enjoy him as an antagonist because he is murderous jerkass with few sympathetic traits, and see his horrible behaviour as necessary to set up the tone of the story and a special and cathartic confrontation between him and Gyuhwan.
To a lesser but still significant extent, Shinyeong Kang. Many fans enjoy her due to her relationship with Gyuhwan (which is ripe for Shipping), and for being genuinely badass and a level-headed and good person. However quite a few fans are not so pleased, especially due to her distrust towards Zero, even convincing Gyuhwan to abandon him to the MM troops in the final few chapters, and her positive moments coming across as Character Shilling.
Catharsis Factor: Seongbin being defeated by Gyuhwan is this in spades, and One killing him in Chapter 61 was another one.
Crosses the Line Twice: The story runs on this. The first chapter is the protagonist dreaming of shooting up his school and things only escalate from there.
Jerkass Woobie: The Variants may be brain-eating predators, but they are so by nature and not choice, and their brutal treatment at the hands of the MM Corporation is heavily implied to be the reason why the ones we see are particularly agressive and ruthless. Special mention goes to Four, who was once a valiant firefighter who had only killed a single person in self-defense, before learning to hate humans after all he went through.
SeongbinYu is such an unsavory young man, it's near impossible to know when he crossed. If he didn't cross it with the severe bullying he subjects his classmates to, he crossed it when he tried to murder Gyuhwan for talking trash to him. If not, Seongbin crossed it when he beated Zero's and Chayeong's heads open. Seongbin may have crossed it long ago, when he murdered his brother, however the circumstancesaround it make it somewhat tragic.
The Variants crossed during the talent show massacre. Individually, Four crossed when he killed Mrs. Ahn, and One crossed when he reveals that he devoured many of his own kind for power.
The now-deleted sequence where Gyuhwan dreams of shooting up his school, both due to setting up the series's premise, and the aforementionedMemetic Mutation.
Viewer Gender Confusion: Zero can easily be mistaken for a girl (even Chanhyeok calls her one.) However, Sangjin Kim refers to Zero as a boy. It is possible, however, that Zero just changed his appearance.
