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Our hero. Formerly the class clown, Akira now finds himself forced to lead his classmates through an island filled with deadly animals.
- Accidental Pervert: The most frequent gag is him ending up in a compromising position with a girl, and Rion dragging him off by his ear.
- Badass: Coming in just behind Yarai and Kouhei.
- Big Eater: Though it hasn't really come up since the first chapter.
- Book Dumb: Before coming to the island, Akira was generally not bright and scores low grades at schools
- Celibate Hero: Seems to be his primary reason for not acting on his feelings for Rion. They're more than a little busy.
- Can't Act Perverted Toward a Love Interest: He like peep on the girls, but not Rion.
- Childhood Friend Romance: With Rion.
- Chivalrous Pervert: Despite being called a pervert, he always acts like a good guy to the girls on the island.
- Class Clown: Before coming to the island. Which is why pretty much everyone is shocked when they find out he's the one leading the most successful group of survivors.
- Clueless Chick Magnet: His charisma and leadership abilities have also made him the romantic target of Rion Akagami, Maya Miyauchi, Tokiwa Aya, Yuki Sakuma, Kagura Mami, Kanako Oomori, Rei Ooguro, and Kashiwagi Sanae, who considering him to be an ideal husband should they be unable to leave the island.
- Determinator: He has a resolute and determined personality which always places his friends priority over himself and attempts to to save anyone close to him, regardless of the situation.
- Disappeared Dad: Chapter 183 reveals that he died of an illness when Akira was four.
- Get a Hold of Yourself, Woman!: Do this to Yuki...slapping her butt.
- The Hero: Might as well have it stamped on his forehead. He's not afraid to try and save everyone, including people that would consider him as an enemy. Throughout the series, whenever Akira has a plan despite the danger, he would always put himself in the front of the danger.
- The Leader: A mix of types III and IV. He is a capable leader, many times due to his leadership his group is able to survive with minor losses.
- Living Emotional Crutch: Some of Kouhei's inner dialogue suggests that Akira is this to him.
- Magnetic Hero: He's not the strongest or the smartest, but he's very good at gathering friends. Best highlighted when Akira asks for volunteers to go to the pyramid, -a mission that will take a week to get there, and where there is a potentially dangerous doctor capable of spreading a plague- everyone raises their hands.
- Took a Level in Badass: As time on the island progress, his fighting skills have progress to the point that he could fight evenly with Kouhei. Even able to dodge Kouichi’s blows. Due to his competence, his group is able to muster up courage and feel calm.
Akira's childhood friend.
- Action Girl: As a gymnast, she isn't to be underestimated.
- Buxom Is Better: No one makes any secret why they find her the most attractive schoolgirl.
- Childhood Friend Romance: With Akira.
- Clingy Jealous Girl: Doesn't appreciate the fact that other girls like Akira too.
- Genki Girl: As genki as is possible when you're on an island filled with hostile wildlife.
- The Glomp: Rion is not subtle with her joy at Akira being alive.
- Hair Decorations: Two ribbons holding up her hair, based on a similar pair Akira gave her as a child.
- Ms. Fanservice: Share the role with Oomori as main source of Fanservice.
- School Idol: Gymnastics, specifically.
- Victorious Childhood Friend: Slightly implied at the end. Very unclear though (and likely on purpose).
- Zettai Ryouiki
The school prodigy and the first person Akira meets after crashing.
- Awesomeness by Analysis: He is very analytical and observant with a great memory, able to recall even subtle or seemingly-insignificant pieces of information
- Badass Bookworm
- Chick Magnet: Subverted. He came in first with 6 votes during the girl's popularity contest, but it seemed that it was planned by the girls.
- Infinite Laptop: He carries around a foot pedal peripheral to keep it charged.
- Intelligence Equals Isolation: At least until the plane crashed.
- Jerk with a Heart of Gold: He can be rather callous, but he ultimately has the group's best interest at heart and will risk his life for the safety of his friends.
- The Lancer: To the point where Akira designates him as the leader when he leaves to explore the pyramid.
- Missing Mom: What finally gets him to empathize with Zaji.
- Mr. Exposition: With his laptop and database, he's the one who is usually in a position to explain everything.
- Nerd Glasses: Has large square glasses with the white brim on most of the time.
- The Smart Guy: Shirou more than makes up for it with his high intelligence. He is extremely knowledgeable in various fields of science, especially prehistoric creatures and extinct animals, which makes him an asset to his friends and comrades. His knowledge is not limited to just prehistory and its wildlife and fauna; he is knowledgeable in world history and historical figures, etc.
- The Short Guy with Glasses: He is a guy of a short stature.
- Teen Genius: He is highly intelligent and has been the school prodigy since elementary school.
- Took a Level in Badass: After Zaji's death.
A clumsy stewardess who Akira meets after crashing.
- Big Breast Pride: She views her large breasts as her only redeemable feature since she feels she's too clumsy to be of use to anyone.
- Buxom Is Better: Most of the male characters are attracted to her large breast.
- Oomori herself think that Akira could be seduced with her large breasts.
- The Chick: While she does her best to be useful, she's frustratingly aware that she can't contribute as much as the others.
- Dojikko: She insists that she is too clumsy to be helpful. Kanako is constantly seen tripping over throughout the series.
- Friend to All Living Things: Well, the squirrel-creatures, anyway. Everything else is far too violent.
- Fur Bikini: Wears one in the finale with a definite Cat Girl vibe.
- The Medic: She only has basic first aid training, but that's better than everyone else.
- Meganekko: In Chapter 4. Usually she wears contacts.
- Ms. Fanservice: Share the role with Rion as main source of Fanservice.
- 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.
- Sexy Stewardess: She is a beauty stewardess and for nearly all the story wears her flight attendant uniform.
- Statuesque Stunner: She is pretty tall.
- Team Mom
- Took a Level in Badass: At first she breaks down quickly and is scared to death of a small and furry animal, but later she takes a stab wound from Kouhei and tries to write it off as nothing.
Kazuma "Zaji" Saji
A boy from class 3 who Akira's group meets on the beach.
- The Big Guy: Not anywhere near as good a fighter as Yarai or even Akira, but definitely strong and tough.
- Chivalrous Pervert
- Friend to All Children: Back home he was never good with kids his age, but acted as a big brother to the neighbor kids.
- Likes Older Women: Absolutely shameless about his attraction to Oomori.
- Missing Mom: She left her family for another man.
- Sacrificial Lion: Dies from internal bleeding.
- Never Found the Body: Due to falling off a cliff off-panel.
A notorious delinquent from class 4.
- The Ace: He isn't perfect, though. His leadership skills could use some work, and he refuses to take orders from someone else. However, these traits keep him from taking up the limelight too much.
- Badass: Yarai has been shown to have an unknown ferocious, massive amount of strength that he uses in a variety of ways. Aside from being able to sends humans literally flying with his kicks, he has been shown to be strong enough to rip a large claw off a Chalicotherium and also flick a coin at an Arsinoitherium with enough pressure to cause it to stop in its tracks. He is able to be able to defeat a group of animals simply by himself showing he's extremely effective in combat, being able to defeat humans and animals alike. He's able to injure an animal using keys as a weapon easily showing off his inhuman strength.
- Even Bad Men Love Their Mamas: Granted, he's not exactly a bad guy, but the reason he's so attached to Kurusu-sensei is that she reminds him of his (deceased) mother.
- Face of a Thug: Some girls note that his face looks like a serial rapist's, and in color pages his eyes are yellow.
- Friendless Background: Segawa points out that Akira is his first real friend.
- Genius Bruiser: Much smarter than he lets on.
- Heroic B.S.O.D.: Has one when he loses to Akira.
- Huge Guy, Tiny Girl: With Kurusu-sensei.
- Improvised Weapon User: His weapons of choice are car keys and 500 yen coins.
- Jerkass Façade: 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.
- Love Letter Lunacy: Led Saki Segawa to think he had a crush on her.
- Love Triangle: It remains to be seen whether or not he is in one with Kurusu and Segawa.
- The ending both confirms and resolves this. Everyone assumes Yarai and Kurusu are a couple but point out nothing has happened because Segawa is always around to interfere.
- Men Don't Cry: Averted in Chapter 141, where Saki points out that he's crying because doesn't want to kill Akira.
- Missing Mom: Twice, at that!
- Mr. Fanservice: To recap: Yarai is tall, blonde, strong and has highly defined muscles and a big chest that make him the physically biggest character in the series. He has many Shirtless Scene and get a double-page where he bath naked.
- The Rival: Sees himself as such, though he and Akira are on much better terms than many other rivals in anime.
- Single-Target Sexuality: The only person he shows any remote interest for is Kurusu sensei.
- The Stoic: He hasn't shown any signs of finding his current situation disturbing yet remains relatively calm throughout the whole ordeal.
- Not So Stoic: 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.
- Sugar and Ice Personality
- Younger Than They Look: 14 years old, ladies!
The homeroom teacher of class 4.
- A-Cup Angst: This
- Adults Are Useless: To a degree. Her heart's in the right place and she is often very comforting. But there are plenty of times where she needs rescuing by her own students.
- Animal-Eared Headband: Yarai told her that it would protect her from animal attacks and she believed him.
- Attempted Rape: The victim of it in the midst of the panic on the plane. Morita's video reveals that Yarai saved her.
- Beauty Is Never Tarnished
- Hartman Hips: She has a small chest and waist, but her hip size is huge compared to the other females of the series.
- Hot Teacher
- Huge Guy, Tiny Girl: With Yarai.
- Ill Girl: The first to contract the eye disease. And now Nishikiori's revealed that she has internal bleeding.
- The Load: She tries, bless her heart, but she's not that good at it.
- Love Triangle: It remains to be seen whether or not she is in one with Yarai and Segawa.
- Mortal Wound Reveal
- Secretly Dying: Inverted. Her companions know, she doesn't. However, it appears she's figured out the truth on her own.
- Meganekko: She is usually seen with glasses on, which are also coloured black.
- Nice Girl
- Sensei-chan: Motoko is a female teacher of small stature for her age, but very cute and nice. She worries about all her students and when one doesn't offer any enthusiasm in class, she tries to introduce them to do more things.
A girl from a rich family who dislikes Yarai.
- 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.
- Anguished Declaration of Love: To Yarai, when it seems like he sees Motoko as a love interest rather than just a teacher.
- The Glomp: After Yarai saves her.
- Just Friends: She suggested this to Yarai in response to his love letter. Since he never actually sent her a love letter, he had no idea what was going on.
- Love Confession: In the backstory, she thought Yarai was trying to give her one. Turns out that because the letter was unsigned, she had made a big mistake.Yarai: I feel bad for the guy who wrote that letter.
- Love Letter Lunacy: Led her to think Yarai had a crush on her.
- Love Triangle: It remains to be seen whether or not she is in one with Yara and Kurusu.
- Non-Human Sidekick: In Chapter 115, she picks up a turtle and declares that it will be the group's dinner. In Chapter 133, we see that she's kept him and named him "Mr. Lucky".
- The Ojou
- Taking The Punch: Takes a punch from Yarai intended for Akira.
A girl who has joined Yarai's group with Saki. Other than the fact that she is good at encouraging others, not much is known about her.
- Letting Her Hair Down: In the finale
- The Load: Hasn't really done much in the hundred chapters since her introduction.
- Those Two Girls: With Machika.
- Tomboyish Ponytail: Again, there's not enough detail about her personality to know how much she fits.
A girl who has joined Yarai's group with Saki. Originally mistrustful of Yarai, but she's been warming up to him.
Akira's Extended Group
A 10 year old girl (or not) in control of a group of 30 men. In reality, "she" is actually a body double for the real Miina Isurugi.
- Chekhov's Gunman: First seen running with her back to the camera on Eiken's Apocalyptic Log.
- A Child Shall Lead Them: Miina is first completely introduced as the boss of an Adult Camp. The yakuza worked as his boyguards. At that time he is still working on his act as the real Miina Isurugi.
- Deadpan Snarker
- Fan Disservice: She is very fond of squicking everyone out.
- Girlish Pigtails: Miina has long blonde hair tied into twin ponytails.
- Harmful to Minors: Witnessed his group's assault and murder of Towa-senpai.
- Little Miss Snarker: For any given value of "Miss", anyway...
- Loli: Played for Laughs. She flashes her panties, poses seductively, and all in all does everything see can to turn on men who know "she" is actually a boy.
- Manipulative Bastard/Guile Hero: The former being how she accomplishes the latter. Throughout the series, Miina has shown to have a great ability at maniuplating people in all types of different ways, pretending to be something he isn't. Shirou Mariya had stated he has a great amount of nerve for being able to do so, able to act as someone he isn't.
- No Name Given: Eventually is later revealed to be Heijiro.
- The Sixth Ranger
- The Tease: A "squicky" version. He makes quite a few perverted jokes and teases Akira Sengoku rather easily throughout the series.
- Unsettling Gender Reveal:
- The first time, when the group escaped from the adults, she pulled off "her" panties without warning to make sure she got her message across.
- The second time was when she and Rei went to bathe together. Implied to be set up by the boys as a prank on Rei.
- Wholesome Crossdresser: "HE" is a young actor who was prior to the plane crash, was hired to dress up as the real Miina Isurugi. He like this role and not care what other people say about him dressing up as a female.
A student from another school who became famous due to her supposed psychic powers.
- Buxom Is Better: Suzuki sure think this of her.
- The Cassandra: Twisted around. Her manager was faking her visions and killing to make them come true, but never believed Mami's real visions. Thankfully, Sengoku is willing to hear her out.
- The Load: During Piramid Arc, due falling debris, Mami injured her leg and had troubles to keep up with others and so couldn't climb down to laboratories. When Akira's Pyramid Party escaped from the Pyramid, Mami was the only one who got caught.
- Nice Girl: Quiet, gentle, and friendly at all times. Despite her quiet nature, she's is kind to others and does things in the best interest of others.
- Seer: She can see the future with an 80% success rate. She can also predict events that have yet to happen for numerous weeks, as seen when she predicted Akira having a scary face.
- Shrinking Violet: Mami is a relatively shy, meek girl. She is doubtful in her own abilities and is usually seen hesitant. She doesn't seem to laugh much, but when she does it's a cute giggle. She doesn't seem to have any outgoing personality and is more reserved and extremely embarrassed when brought up in certain situations, especially with guys.
The class representative of class 4, Yuki was always scolding Akira for goofing around. Initially a member of Kouhei's group, she joins Akira's group after being rescued from drowning.
- Agent Mulder: Yuki has been shown to have certain addictions or sorts, that when she likes something, she'd think unimaginable things and when she believes in something, she'll try to influence others into it, too. For example, because of Yuki's love for bears, she imagined the island would be in the shape of a giant bear and when people were debating about Mami Kagura's precognition abilities, she influenced Kanako Oomori into believing they were real, knowing a variety of facts about ESP abilities.
- All Love Is Unrequited: Has started falling for Akira, well aware he is head-over-heels for Rion.
- Class Representative: At school, Yuki had been the class president and was always nagging a few of her fellow students because of misbehaviour, especially Akira.
- Hair Decorations: Two blue hair clips.
- Ms. Exposition: Yuki is extremely intelligent and knows a lot about various historical facts and trivia and is often seen explaining items, objects or past events that have happened before.
- Oblivious to Love: She doesn't seem to be aware of Yamaguchi's feelings for her.
- Secret Keeper: Is the only one who knows Kouhei is still alive.
- Tsundere: Toward Akira.
The student council president. Initially, he is working with his group to build a school on the island. However, once Akira reveals who assaulted Miina, he and his group decide to join Akira's.
- All Love Is Unrequited: Has feelings for Yuki, who seems to be interested in Akira despite knowing full well of his feelings for Rion.
- The Leader: He seems to be confident in his own leading abilities, yet isn't embarrassed to relinquish his position when need be. He has shown to be an exceptional leader and in reality, was the first group to create a base intended to be for everyone.
- Megane: He is usually seen with his white brimmed spectacles.
- Nice Guy
- Student Council President: A classic example.
A childhood friend of Zaji's and an initial member of Yamaguchi's group.
- Action Girl: Is the most action-oriented of the girls. She is a skilled and confident warrior, able to smash various targets to pieces with her kicks, and has such control she could lash out a leg toward someone's head and stop abruptly before making contact. She is also agile and has a tolerance for damage.
- Alliterative Name: Both start with "M".
- All Love Is Unrequited: Believes Akira would make a good husband.
- Badass: Heir of a martial arts dojo, she is possibly the strongest female within the group and not afraid to fight monsters more than twice her size or fight adults with well seasoned abilities.
- The Big Guy: Takes this role after Zaji's death.
- Jerk with a Heart of Gold: Despite being rather self-absorbed and arrogant whilst loving a fight, she does care dearly for her friends and commonly takes the situation up herself no matter the danger.
- Kick Chick: Often attack whit her kicks, but she know like use the first too.
- Lovely Angels: Becomes this with Aya Tokiwa in the finale.
- Panty Fighter: She often attack with kicks and, wearing a short skirt, show her panties become inevitable.
- Pervert Revenge Mode: Corners a pair of peeping toms alongside Aya in the finale and threatens to kill them.
- Tomboy: She is often considered a delinquent with her love to fight and talks with masculinity.
- Tomboyish Ponytail: She has long brown hair that she a majority of the time ties in a ponytail without the use of an actual ribbon or such.
- Tsurime Eyes: Highlighting her aggressive nature.
- Vigilante Man: Forms the Vigilante Corps with Aya.
- Why Did It Have to Be Snakes?: Is terrified of insects.
Ryouichi SuzukiA member of Yamaguchi's group. An unrepentant lech.
- Bastard Boyfriend: He has very little interest in his girlfriend except for sex.
- Born Lucky: This is seen by the fact at how he survives numerous dire animal attacks and leaves realtively uninjured.
- Covert Pervert: Without the covert part. He tried to rape Rion and fantasizes about a six-some with the group's most attractive girls.
- Jerkass: Suzuki spends of his time being an arrogant, manipulative pervert. He almost raped Rion, and later left Sengoku for dead to have her for himself.
- Manipulative Bastard: Suzuki is well known for his rather dark demeanour being able to easily manipulate others to qwell his own fantasies and ideas. He is well known for lying to make himself seem better and often considers himself quite highly being arrogant in a way.
- No Guy Wants an Amazon: The only girls he doesn't get a hard-on for are Maya and Aya.
- Sinister Schnoz: He has a huge nose, and is the most repugnant of the boys.
- Token Evil Teammate: Also Akira not trust him.
Shizuka HatsuseShe was the vice president of the school student council and member of Yamaguchi's group.
- Photographic Memory: Thanks to her eidetic memory, she can memorize anything she sees without trouble and therefore lead to her strong personality and knowledge.
- The Smart Girl: Shizuka has an amazingly vast amount of knowledge and resources, easily able to understand and come to terms with things others may not. She understands a massive variety of things from how DNA works to how plants survive and live.
A 20-year-old university student and a childhood friend of Tooru.
- Absolute Cleavage: Her clothing leaves extraordinarily little to the imagination. She wears a black bra and her body is mostly exposed only with a dark long-sleeved red top that exposes her stomach and breasts whilst ending at her elbows.
- Cool Big Sis: She act as this to other girls because she is one of the few characters attending university.
- Cosplay Otaku Girl: Her profile indicates that she is this, and she actually has an eyepatch she uses for cosplay with her.
- Cute Little Fangs: She has two front teeth more noticeable than the others on each side of her mouth.
- Genki Girl
- Hard-Drinking Party Girl: It is shown in a flashback.
- Lovable Sex Maniac: Outside of her happy demeanour, she also seems to have a blatant perverted side about her. She is commonly shown lying to the girls within Akira's Group, as shown telling them about numerous lies about her having different types of adult experiences and giving them nonexistant tips which ultimately were lies. This doesn't end as she has been shown going off at the guys for doing certain things and actually rounds up the girls to do the same thing because she had thought it was interesting. She is commonly fun-loving and her perverted acts are all done in good jest.
- Ms. Fanservice: She often invoke this status, but most of the boys are interested in the girls their own age and the adult men are lolicons.
- The Tease
- Tomboy: Rei has a tomboyish, upbeat demeanour about her continually being uplifting and happy when around others.
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.
- Death by Flashback
- Dropped a Bridge on Him: Dies in the last arc, a few chapters from the end.
- 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.
- Secretly Dying: Save Rei by the collapse of a ceiling. 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
- Nice Guy: When first introduced, Tooru was believed to be quiet and intimidating, refusing to say anything, however when he takes off his bandges his personality is revealed to be both more open and friendlier.
- Number Two: When Akira is gone, Tooru is usually the one left in command or as a leader for the group realising things that others may not.
- Team Dad: Because he openly confronts people, other groups have mistook him for the leader at first glance considering he's an adult and has the personality of one.
Makoto "Eiken" Morita
A friend of Akira's. Enjoys taking perverted pictures of girls.
- Blinding Bangs: As demonstrated in his picture.
- Camera Fiend: Generally used to get pictures of the girls. However, he was able to use the zoom from atop the mountain to spot the Antenna Tower.
- Sherlock Scan: He has a keen eye for details.
A girl from class 2 and a member of the track team.
- Action Girl: She is very action oriented and fights with a sharpened stake and her legs.
- All Love Is Unrequited: Agrees with Maya's belief that Sengoku is the only suitable marriage candidate.
- Badass: One of the rare girls to fit this description.
- Berserk Button: Has a sensitive spot on her back and hates having it touched.
- Blood Knight: She's referred to fights as fun—you know, the fights against the several hundred pound wild animals that they don't so much defeat as survive.
- Emotionless Girl: She doesn't really talk much, so we can't be sure what she's thinking.
- Hair Decorations: Her headband.
- Lovely Angels: Becomes this with Maya Miyauchi in the finale.
- Pervert Revenge Mode: Corners a pair of peeping toms alongside Maya in the finale and threatens to kill them.
- Vigilante Man: Forms the Vigilante Corps with Maya.
A perverted monk with no interest in girls over the age of 20.
- Chekhov's Skill: He didn't want to become a monk, but the training he received has saved his life multiple times on the island.
- Enjo Kosai: Was involved in a scandal revolving around this.
- Eyepatch of Power: Sports one (along with a badass scar) in the finale.
- Locked Away in a Monastery: To avoid the aforementioned scandal, his parents made him become a monk.
- Lolicon: Very much so, and of course Played for Laughs.
- Hidden Depths: Yes, he's an unashamed lolicon, but he also gives Sengoku a speech on the nature of evil (specifically, in reference to Nishikiori).
- Pedophile Priest: Well, in this case, an ephebophile monk.
A manager at a successful publishing firm who had thousands of people working under him.
- Adults Are Useless: His skills might be useful for organizing people, except he's too stuck up for anyone to listen.
- Jerkass: He's not happy that he's stuck on an island with a bunch of kids.
The real one. Carries around a sketchbook filled with drawings of extinct animals.
- From the Mouths of Babes: Has been known to lapse into bouts of cursing unbefitting her age.
- Girlish Pigtails: She wears pigtails.
- No Nudity Taboo: Cheerfully takes off her panties to give to her body double without a second thought.
- No Social Skills: Due to being raised in isolation by her grandfather.
- The Ojou: She doesn't act like it due to her amnesia, but she is ridiculously rich, as the only heir to a massive megacorp.
- Overprotective Grandfather: He got her a body double for no explained reason other than paranoia.
- Rescue Romance: Is developing a crush on her body double.
- 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.
- Foil: To Akira, arguably.
- Hidden Agenda Villain: His plans and goals beyond mere survival are a complete mystery. and stayed that way till the end.
- Manipulative Bastard: Tricked Kouhei into killing an innocent girl for no real reason.
- Mysterious Stranger: Other than the fact that he's a student, little is known about him.
- Names to Run Away from Really Fast: He introduces himself as Hades, King of the Underworld.
- The Social Darwinist: He's the first one to introduce Akira to the "survival of the fittest" mentality.
- What Happened to the Mouse?: The manga ends without revealing what happened to him.
Akira's best friend, and a popular boy on the volleyball team.
- The Ace: Good at pretty much everything, and immediately gained a large group of followers when they left the plane.
- All of the Other Reindeer: Initially picked on because of his curly hair. When Akira called it cool, the other children agreed and soon Kouhei became popular.
- Beauty Mark: A mole under his eye.
- Broken Ace: Slowly starts to go off the deep end after killing the pilot during a mass panic.
- Easily Forgiven: Sorta. Although Akira saves his life and still considers him his best friend, he agrees that what Kouhei has done is unforgivable.
- Redemption Equals Death: He gave up the possbility of run from death with Akira and Rion and choose to die as punishment for his actions.
- Came Back Strong: Turns out Hades found him in a near-death state and saved him. And he aided Akira's group without revealing his identity by grabbing a giant monster and pulling it down a hole.
- Power Born of Madness: As Hades puts it, his current mental state allows him to do feats no normal human can do.
- Murder Makes You Crazy: This is what breaks him, combined with a series of misunderstandings and some light brain damage.
- These Hands Have Killed
- Walking Spoiler
- What Happened to the Mouse?: The manga ends without revealing what happened to him.
Daigo YashiroA man who was travelling around the island with Junichi Mutou. He was originally part of the group that took refuge in the pyramid and was travelling around the island to find the mysteries behind it. However, he later escaped after Takashi Nishikiori took reign over the group.
- Badass in a Nice Suit
- Good Smoking, Evil Smoking: He is one of several characters who smoke.
- Screw This, I'm Outta Here!: He escaped from the Pyramid after Takashi Nishikiori took reign over the group; he is really disgusted by Nishikiori evil acts.
- Would Hurt a Child
- Yakuza: Subverted. Because of his business suit people think he is with the Yakuza, but in chapter 155 he says that before the island he was a writer.
- My Greatest Failure: In the past he was not capable to save his son, so he had hidden the fact that he was the doctor.
- The Reveal: After Nishikiori had revealed that he wasn't doctor at all, with Oomori's and Akira's knowledge, they managed to deduce that Junichi was the doctor indeed.
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.
- Beauty Is Never Tarnished: He freaks out when he thinks he might end up with a scar on his face.
- Big Bad: Of the final arc, even with the more dangerous extinct animals, he holds the morale threat
- Deadly Doctor: He uses his medical skills to inflict maximum pain without leaving any lasting injuries. And he's not even a real doctor!
- Karma Houdini: Survives at the end, although loses a leg.
- Living Lie Detector: Through a combination of checking someone's pulse and pupil dilation.
- 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.
- Shadow Archetype: To Sengoku.
- Smug Snake: Generally, his plans work perfectly, so he doesn't quite fit this. But when they don't (such as his various plans to kill or control Akira), this comes out full force.
- The Sociopath: Laughs as a man and daughter die in front of him from a disease he caused.
- Tyrant Takes the Helm: He wrested control of the Pyramid group away from the aforementioned father.
The school science teacher, and a member of the Pyramid group. That is, until Nishikiori had him beaten and thrown in prison.
- Badass Teacher: Not physically, but he is willing to go to absurd lengths to protect his students.
- Chivalrous Pervert: He has a perverted side as he's seen reading an erotic magazine during a school trip despite students being around him.
- Mad Scientist: He has been a science teacher for an unknown amount of time and some students refer to him as the mad science teacher. Akira mentioned that Ugen tried to made a rail gun at their school once.
- Smoking Is Cool: Where he keeps getting the cigarettes is less clear.
- Stuff Blowing Up: His specialty thanks to his knowledge about the different chemical reactions and how they form together.
- Ultimate Job Security: Despite blowing up his classroom on a regular basis, he was never fired. None of the students know why.