* AngstWhatAngst: 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 [[spoiler: 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.
* EpilepticTrees: Everything in the series.
* FanPreferredCouple: If the forums of various sites are to be believed, then Akira/Rion is by far the most popular pairing, and for good reason, due to their willingness to protect and take care of each other, no matter what happens. Akira/Mami seems to be gaining popularity quickly, though.
* FetishRetardant: How some feel about the fanservice.
* HoYay: Kouhei ''really'' wants to find Akira. [[spoiler: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 [[spoiler:''cries'' because he doesn't want to kill Akira, but Nishikiori won't save Kurusu-sensei if he doesn't.]]
* MartyStu: Akira.
* MoralEventHorizon: [[spoiler:Kouhei]], up to then one of the nicer characters, kills a girl on the mere suspicion that she saw him stab the pilot.
** [[spoiler: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.
* NightmareFuel: Being stuck on an uninhabited, mysterious island with [[EverythingTryingToKillYou every large and dangerous prehistoric species out to eat or maim you]] is ''not'' a Happy Fun Time. So you can bet that the series is full of this.
** 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.
** [[http://www.mangahere.com/manga/cage_of_eden/v17/c143/19.html This]] [[EldritchAbomination creature]] qualifies
*** [[http://www.mangahere.com/manga/cage_of_eden/v17/c150/13.html This]] looks more like a demon than an extinct animal
** [[spoiler:Nishikiori]]'s brainwashed slaves, who keep serving him despite all logic and reason.
* {{Squick}}: In general, the manga doesn't pull any punches in showing ''exactly'' what teeth[[note]]or beaks, or claws, or [[EverythingTryingToKillYou everything else]][[/note]] bigger than your head can do to you...
** Or big falls.
* TearJerker: Several moments in the series.
** [[spoiler: Akira's mother dealing with her son's presumed death.]]
* TooCoolToLive: [[spoiler:Zaji]]