The Medic: She only has basic first aid training, but that's better than everyone else.
Meganekko: In Chapter 4. Usually she wears contacts.
Schoolgirl Lesbians: The reason she became a flight attendant (in spite of failing the test 16 times) was to be with her former senpai, who was her first love. She insists that it was because she went to all-girl school and that she likes men now.
Jerkass Fašade: He was always a nice guy, but because but because of his looks, everyone thought he was a jerk and a delinquent, so he decided to play that role. Only his mother and Kurusu-sensei treated him for being him, rather than going by his looks.
Nerves of Steel: Subverted in Chapters 15 and 64, where he laughs at Akira being attacked by the Edwardsi and at the misunderstanding that led Saki to hold a grudge against him. In Chapter 141, he cries because he doesn't want to kill Akira, but Nishikiori won't save Kurusu-sensei if he doesn't.
A-Cup Angst: While she's not small, she's smaller than Rion, and well aware that this is why the latter is considered prettier.
All Girls Want Bad Boys: Played with. Due to the love letter confusion, she had a small crush on Yarai, which went out the window when he tore up her letter (biiig misunderstanding). On the island, once she realizes what actually happened, she starts falling for him harder.
Spoiled Sweet: Doted on by her ridiculously rich grandfather, to the point that she had no social skills. With her memory gone, she rarely speaks, so it's hard to get a good read on her character.
Trauma-Induced Amnesia: The improbability is heavily lampshaded, increasing the possibility that there's something more to it.
Waif Prophet: She knows quite a bit about the extinct animals on the island, even stuff not in Mariya's encyclopedia.
Other than the fact that he is a student, little is known about him, since he refuses to take off his mask. He introduces himself by banging Akira on the head with a rock, then suspending him off a cliff.
Cheap Costume: The mask probably cost him a thousand yen, tops (fifteen dollars).
Cool Mask: It's just a cheap souvenir from Guam, but he makes it work.
Transsexual: Quite possibly. It's increasingly hard to tell how much of his identification as female is because he likes screwing with people's heads, and how much is because he genuinely feels more comfortable that way. It's certainly notable how little things change once everyone knows his secret, and he has no reason to hide it any more.
Ms. Fanservice: Subverted. She tries, but most of the boys are interested in the girls their own age, and the adult men are lolicons.
A university student and childhood friend of Rei's.
Beauty Is Never Tarnished: A complicated example. He covered his face because he was ashamed of his scars, and his girlfriend started ignoring him. Once she is officially out of the picture, he takes off his bandages and reveals that he was just overreacting.
Secretly Dying: Claims he's ok under the rubble. Turns out he's actually been crushed and bleeding profusely and knows it, he lied just so Rei wouldn't worry
Good Scars, Evil Scars: First introduced with bandages covering his face because he's ashamed of them. During this time, he is silent and rather off-putting. Once the bandages come off, the group quickly points out that the scars actually look pretty cool. Tooru himself becomes much more open and friendly.
A doctor who holds the Pyramid group in thrall.
Asexual: Somewhat implied. It's established quite a few times that he had no interest in the female hostages. When asked what types of breasts he liked, he replied "neither." He might be interested in the other gender, but nothing in the story ever suggested that.
Manipulative Bastard: Has managed to turn the entire Pyramid group into his willing slaves through careful manipulation of groupthink and other psychological tricks.
Morally Ambiguous Doctorate: Whoever gave this man a medical license needs to be shot. Then again, he doesn't actually have a medical license.
A Nazi by Any Other Name: He is explicitly referred to as using Nazi tactics. However, in a rare example, they are not talking about genocide or racism (the population is too small for that). Rather, he borrows the Nazi "whistleblowing" tactic, encouraging his slaves to report on each other. Not only does it keep him informed, but it keeps his followers scared and unable to cooperate against him.
Plague Master: Spread a disease among the Pyramid group and only gave people the cure when they swore loyalty to him.
Politically Incorrect Villain: On top of everything else, he's a misogynist. The only reason he's not a rapist is because he thinks women are so far beneath him as to not bother.