WARNING: As is common with the Infinity series, a lot of these tropes are by their merely being listed next to characters here, spoileriffic. The worst cases are in a special Spoiler Characters folder that leaves all spoilers within it unmarked, but a lot of others still have major spoilers that are marked next to trope names that aren't. You have been warned.
A 20-year old woman who studies psychology, more specifically mental illnesses. She wanted to travel to SPHIA to study Inubuchi Keiko, but after the plane crash stranded her in the mountain cabin, she is more concerned about keeping the other survivors alive. She frequently swaps bodies with Satoru, and as a direct consequence has to deal with his problems at SPHIA too.
- Driven to Suicide: In one Bad Ending, where she feels she's responsible for Yuni and Yomogi's deaths.
- "Freaky Friday" Flip: With Satoru and the male twin.
- Meaningful Name: Kokoro means "heart" in Japanese. And indeed she fits The Heart archetype.
- Mistaken for Gay: For a brief moment, Satoru contemplates whether she has "other tastes".
- Red Oni, Blue Oni: Red to Satoru's Blue.
A 21-year old amnesiac who might have been an employee at SPHIA. He doesn't really remember due to being shoved down the clock tower and losing all but a few key memories, and ever since he's trying to find out who is the one attempting to take his life.
He swaps bodies with Kokoro at irregular intervals, and has therefore also to deal with the situation in the mountain cabin.
- Ascend to a Higher Plane of Existence: One theory states that the original Satoru, I, became one with "Self" at the beginning of the game, after he fell off the clock tower.
- Enmity with an Object: Wristwatches. Particularly Kokoro's. He notes that he finds pocketwatches to be more gentlemanly and considers the weight of a wristwatch to be oppressive. Every single time he's in Kokoro's body, he takes it off and places it somewhere else (Usually somewhere it wouldn't be expected to be). Kokoro actually becomes convinced that he's intentionally trying to make it hard for her to find it, but there's really only evidence of that in Satoru's route the final time Satoru hides it.
- "Freaky Friday" Flip: With Kokoro and the male twin.
- Laser-Guided Amnesia: Though he tends to remember a bit more than most examples.
- To elaborate: He only remembers the facts that Kokoro knows from her route — for example, he remembers his break-up with Lin, but not their relationship.
- Mad Scientist: His past, true self had traits of this.
- The Man Behind the Man: Behind Enomoto and Yuni, and his body is actually the former's. It is also assumed that his mind is, in fact, not Satoru's (I), but "Self", (I, the player), and therefore only remembers those facts that the player learned about him from Kokoro's route.
- Memory Gambit: It turns out his past self, I, is the true mastermind behind the events of the game, and took his memories with him while implanting a few in the new Satoru's mind.
- Morality Pet: To Lin.
- Red Oni, Blue Oni: Blue to Kokoro's Red.
- Talking to Themself: Happens in Bad Ending #28.
- The Smart Guy
- Tomato in the Mirror: It turns out that the body he's inhabiting is actually Enomoto's. The Infinity Series Timeline explains that the two of them switched bodies via quantum teleportation in July 2011, but the reason is never given.
An 11-year old boy whom Kokoro met on the plane, and one of the survivors of the crash. Curiously enough, there's two of him: one in the mountain cabin (who continuously makes cryptic remarks about their situation), and one in SPHIA (a scared boy who nevertheless becomes friends with Hotori).
- Cheerful Child: Zig-Zagged. He acts liek this most of the time, but also acts like a Creepy Child sometimes.
- Death of a Child: In one bad ending, Yomogi descends into madness and after Yuni doesn't listen to one of his commands, he grabs Yuni by the throat and breaks his neck. In another bad ending, he freezes to death and Kokoro is so filled with remorse that she lays down in the snow and intentionally dies of exposure. And in another, he dies of hypothermia and she slits her throat as an act of atonement.
- Improbable Infant Survival: Yuni's obviously not an infant, but he usually survives all the bad endings that result in Kokoro or Satoru being killed.
- Missing Mom: Late in Satoru's route, he says that his mother is no longer around, so he considers Utsumi to be a mother figure.
- Obfuscating Stupidity: The Yuni at the cabin is from the future, and already knows everything that's going to happen.
- Precocious Crush: A couple of different times, he tries to flirt with Kokoro. Although a lot of these are just played off as jokes, during one of Kokoro's Bad Endings, he does a serious Dying Declaration of Love to her.
- Time Travel: He uses the transfers to switch his 2011 and 2012 selves. The one in SPHIA is the one who recently experienced the plane crash, while the one in the cabin is from 2012, a year in the future who used the exchange mechanism to ensure the continued survival of Kokoro and the others.
- Took a Level in Badass: His 2011 self is a scared kid who has no clue what's going on and often lashes out at Kokoro/Satoru. In between the 2011 and 2012 incident, he joins up with Satoru and Enomoto, and after learning everything there is to know about the incident, he matures greatly.
- Zen Survivor: His real '12 self shows traits of this. He's annoyingly reserved with what he reveals to Satoru, but that's partly justified by the fact that Satoru being the one behind everything all along.
A 23-year old rich woman who survived the plane crash, as well as Satoru's former girlfriend. Is a court-appointed lawyer who occasionally quotes parts of the Japanese constitution to support her self-centered opinions.
- It's All About Me: In one of the bad endings, she reveals that she was willing to do anything it takes to survive long enough to see Satoru again, including metaphorically throwing everyone else under the bus, and everyone else can think badly of her if they want as long as she survives this ordeal and reunites with Satoru.
- Arranged Marriage: Has been set up for one by her family, which is the reason she had to break up with Satoru. There's a blink-and-you'll-miss-it scene where she reveals that she blames herself for this; she thinks that she took the "easy way out" by not going against her parents.
- Asshole Victim: In Bad End #8.
- Ax-Crazy: In three different Bad Ends.
- An Axe to Grind: Yes, literally.
- Ice Queen: Suiting her archetype as the "Persona," Lin puts up a front to everyone of being harsh and hyper-critical of everyone and everything. Due to the nature of the plot and her reaction to it - trying to throw everyone else under the bus in order to make sure that she survives - there are only a few moments where the facade falls and her more gentle and fragile traits show.
- The Load: Half of the problems that the survivors of the HAL18 crash have to deal with are instigated by Mayuzumi, and most of the other half are exacerbated by her. There is only one ending where the rest of the party tries to get rid of her, though, and it's not a good ending.
- Psycho Ex-Girlfriend: She is Satoru's former girlfriend.
- Rescue Sex: When Kokoro calls her out on being ungrateful towards Yomogi, she snidely remarks that she is grateful, and that she'll show her gratitude by letting him have sex with her once if they get out of the whole ordeal in one piece.
- The Friend Nobody Likes: Downplayed. While the other characters hates and even tries to get rid of her, Satoru who doesn't dislike her.
- Tsundere: Dere to Satoru, tsun to everyone else in the world.
A 35-year old mountaineer and one of the survivors of the plane crash. It's through his expertise that the others could survive on the mountain.
- Ax-Crazy: His breakdown and behavior in Bad End #8 is truly terrifying.
- It's All My Fault: Blames himself for his son Junichi's death, both for buying the bicycle that got him sent to the Awazumi hospital and for not staying the night with Junichi.
- Luke Iam Your Father: He's Utsumi's husband and the father of one of the kids that Keiko murdered.
- Madness Mantra: "I won't let anyone die any more." in Bad Ending #8.
- Reasonable Authority Figure: Given the circumstances, he's remarkably understanding of Kokoro's strange behavior that she writes off as a "split personality." Also, he's very knowledgeable about what to do to survive in the cabin, is a huge moderating influence on Lin's bitchiness, and provides stability to the much younger Kokoro and Yuni. The only exception is in Bad Ending #8, where he snaps and goes crazy, deliberately letting Lin freeze to death in the basement, breaking Yuni's neck, and behaving very creepily to Kokoro.
- Sadistic Choice: Discussed hypothetically. In one scene, Kokoro asks him which situation he'd prefer to be in: his current situation, where he's trapped in a freezing cabin on a mountain and is running out of food and water, but he's guaranteed to survive at least long enough for the food and water to run out completely...or a situation where he has plenty of food and water and it's warm but a crazed murderer is after him. Yomogi surprises Kokoro by answering that he'd rather have the murderer. Why? Yomogi's reasoning is that as long as he's not too hungry or thirsty or cold to think clearly, he could theoretically change the situation by dealing with the murderer somehow, but he can't significantly alter the situation he's actually in.
A 27-year old woman who works as a therapist in SPHIA. and is responsible for the well-being of the people there.
- But Not Too Foreign: Half-Indian, half-Japanese.
- Dark-Skinned Blonde: Her hair is white though.
- It's Personal: Came to SPHIA to kill Keiko in revenge for her son's death.
- Murder-Suicide: In both of the Bad Ends following her succeeding in her plan to kill Keiko.
- Rescue Romance: Her relationship with Yomogi is the result of this, as he saved her life when he found her on a trip to Nepal.
- Revenge: She's Yogomi's wife and the mother of one of Keiko's victims and came to SPHIA to kill Keiko and avenge her son.
- Roaring Rampage of Revenge/Unstoppable Rage: She flips and tries to kill Hotori towards the end of Satoru's route. In an associated Bad End, she kills both Satoru, Hotori, and herself (and Kokoro, indirectly).
- Stepford Smiler: Outwardly a very considerate and motherly character. Secretly stewing with a desire for vengeance against the woman who killed her son.
- Teen Pregnancy: She gave birth to Junichi when she was 14. The Drama CD makes it clear, however, that this was an accident, and Yomogi immediately took responsibility.
Suzukage Hotori/Inubushi Keiko
A 19-year old girl who has killed 12 people in a hospital in 2009. She has been disagnosed with Dissociative Identity Disorder, so she got acquitted and sent to SPHIA for treatment. Her personality has since then more or less settled on that of Hotori Suzukage, a shy, mute, and generally harmless girl who befriends Yuni.
- Abusive Parents: Speculated to be the cause behind her DID, though it's never confirmed.
- Ax-Crazy: One of her personalities, which is the one that caused the Awazumi Massacre.
- Cheerful Child/Creepy Child: She jumps between both.
- "Freaky Friday" Flip: With Hotori and the female twin.
- Mood-Swinger: May also be this, via Split-Personality Merge.
- Proper Tights with a Skirt: Sports this look pretty much all the time
- Split Personality: Is said to have 11 separate personalities. Her dominant personality is still that of the murderous Keiko, but pretends to be Hotori when she's controlling the body. She undergoes the same body-swap that Kokoro and Satoru do, but with the barely-living body of the real Hotori. Since both transfers are parallel to each other, Kokoro and Satoru only meet one of them respectively..
- Split-Personality Merge: Speculated to go through one shortly before the game's beginning, as she doesn't as much change personalities as changes moods.
- The Voiceless: In Kokoro's route only.
A mysterious man hiding in the control room beneath SPHIA, and the one helping Satoru in advancing his plan. He is also the one inhabiting Satoru's real body, and vice-versa.
Once Satoru finds the secret room, Enomoto explains the details of the body-swap mechanism (which actually isn't), and attempts to kill Satoru after he flips out as a consequence. He is shortly thereafter murdered by the male twin in Satoru's (actually Enomoto's) body.
- Ax-Crazy: Both of the times that he tries to kill Satoru (in SPHIA and in Apoptosis), he seems to relish the idea way too much for it to be considered just part of the job for him.
- Continuity Nod: He is working for Leiblich Pharmaceuticals.
- The Man Behind the Curtain
- Mr. Exposition: He literally shows up out of nowhere in Satoru's route to explain how the transfer phenomenon works, then is killed off almost immediately afterwards by the twins.
- Smug Snake: Treats Satoru with a very condescending attitude, but when it comes down to it, he was merely "original" Satoru's pawn.
- Tomato in the Mirror: The body he's in is actually Satoru's, and vice-versa.
- Villainous Breakdown: Flies into rage when Satoru attempts to destroy the quantum teleportation equipment.
A 19-year old girl and temporary survivor of the plane crash. Shortly before her body freezes to death, she swaps bodies with Keiko, and is thereafter the "Hotori" whom Kokoro meets. She lost the ability to speak as a result of the trauma.
- Death by Origin Story: Sort of. She stays alive for a while in Keiko's (and the female fetus') body, but in the end she's dead for good.
- A Fate Worse Than Death: It's implied that she didn't die immediately in the snowstorm. She was still conscious during the week.
- "Freaky Friday" Flip: With Keiko and the female twin.
- The Ghost: She is never seen, except for one scene in each route.
- Heroic BSoD: Briefly, after finding herself with a bloody knife over Enomoto's body.
- Shrinking Violet: According to the TIPS.
- The Voiceless: Caused by living through the plane crash. She apparently gets better by the end of the game, but loses speech again after surviving the avalanche.
- Tomato in the Mirror: Breaks down upon seeing her reflection (in Keiko's body), but is unable to express her situation to the rest of SPHIA due to the trauma of the crash.
Satoru's sister who is only seen once (twice?), at the beginning of the respective routes.
- All There in the Manual: Practically everything known about her is only taken from the TIPS, Infinity Series Timeline, and speculation.
- Ascend to a Higher Plane of Existence: Possibly.
- Self-Made Orphan: One of her personalities murdered her parents.
- Split Personality: It's implied that the second personality is Keiko.
- Split-Personality Takeover: It's also implied that Keiko did this to her.
Yomogi's and Utsumi's twin children, who were born between the two incidents. They are the respective third personalities in Kokoro's, Satoru's, Keiko's and Hotori's transfer phenomenons and responsible for most of the havoc wrought in both SPHIA and the cabin.
- Ambiguous Innocence: While their actions are very questionable, they literally know nothing, and therefore aren't aware of what they're doing is wrong.
- Death of a Child: The last time we see them, Inubushi is holding the girl on the edge of a cliff with a crazed look on her face. However, as we never see what happens next, we don't know whether this is played straight or subverted.
- Fetus Terrible: Subverted too. As mentioned before, they aren't aware of what they're doing or that it's wrong, and are just acting like babies would if they had adult bodies.
- "Freaky Friday" Flip: The male twins is the "third personality" in Kokoro and Satoru's exchanges; although only Satoru becomes aware of it very late into his route. The female twin is the same for Hotori and Keiko.
- Half-Identical Twins: To the point that even though Utsumi has separate photographs of them, Satoru can't tell them apart and assumes it's just one baby at first.
- Spanner in the Works: To Enomoto.
- The Unintelligible: While we never hear them "speak", the accounts from the others seem to indicate that when they go through their colic, they scream out unintelligibly (justified, as they don't know how to speak).
- A God Is You: Very similar to Blickwinkel in this regard.
- Reality Warper: When "it" sees Sayaka in Satoru's flashback and confuses her for Keiko, Sayaka "dies" and becomes Keiko. It's implied that he warped Satoru's existence and history based on what it knew about him.
- Stable Time Loop: Is caught in one, due to Satoru's plan.