Angst? What Angst?: A lot of the times, the characters will get a little upset but move on rather quickly from the tragic, stressful events around them like discovering that your first love got gang raped to death, finding out your best friend turned into a mass murderer or Zaji dying. Justified in how the characters are constantly in danger and can't afford to dwell too much on the negative things.
Audience-Alienating Ending: The manga was extremely popular during its run until its abruptLeft Hanging ending, and it was likened to Lost in both a literal sense and in unfavorable terms, at which point some were advised to not even bother starting and getting attached to the series.
Complete Monster: Takashi Nishikori crash-landed on an island along with hundreds of other passengers and established his power over them by blackmailing them into serving them, only offering them an antidote to a lethal plague with which they had all been infected if they do so. Killing anyone who threatens his power, Nishikori responds to a confrontation with Akira Sengoku's group by torturing them before sending them on a Suicide Mission. Capturing all the female members of Akira's group, Nishikori forces the males to try to rescue them, while intending to execute one girl for each failed attempt. Trying to force the girls to sentence one of their own to death, Nishikori promises his men they can gang-rape the survivors.
Fanon Discontinuity: Many fans preferred to pretend the ending doesn't exist and treat the plot as a straightforward survival drama.
Fan-Preferred Couple: Akira/Mami started rapidly gaining popularity even though Akira/Rion remained the flagship pairing regarding a protagonist who may as well have had a harem.
Fetish Retardant: How some feel about the fanservice. Panty Shots and Clothing Damage? Hot. On girls who are dead/dying/in serious danger? Creepy. This combined with the occasionally misogynistic atmosphere can make the manga a kind of uncomfortable read.
Kouhei really wants to find Akira. He also states that while he can't bear to show himself in front of Akira anymore, he will protect him from the shadows.
Yarai and Akira have a bit of this, too. In Chapter 141, Yarai actually cries because he doesn't want to kill Akira, but Nishikiori won't save Kurusu-sensei if he doesn't.
Kouhei, up to then one of the nicer characters, kills a girl on the mere suspicion that she saw him stab the pilot.
Nishikiori jumps over the line with every appearance. It really says something when the nicest thing he's done is send a bunch of kids on a suicide mission.
Narm: It is difficult take seriously a dramatic situation while the girls show their panties at readers.
That's not even counting all the humans on the island either. One of the main themes of the manga is that wild beasts aren't the only animals to be scared of.
This looks more like a demon than an extinct animal
Nishikiori's brainwashed slaves, who keep serving him despite all logic and reason.
The Scrappy: Suzuki spends of his time being an arrogant, manipulative pervert. It goes to the point where fans were actually happy when he was attacked by the bird. Several fans were disappointed in chapter 93 when he was attacked by ANOTHER species of bird, but was then spat out.
Squick: In general, the manga doesn't pull any punches in showing exactly what teethnote or beaks, or claws, or everything else bigger than your head can do to you...
creature qualifies