Characters / Oneirosea

• Aloof Leader, Affable Subordinate: As the leader, Ichika is stern and always professional, but she's tasked with wrangling two much less serious subordinates and trying to keep them on task.
• Fighter, Mage, Thief: Hiro, a straightforward swordfighter who struggles to learn the more complex mist-manipulation abilities, is the fighter; Ichika, who prefers to attack with ice from a distance, is the mage; and Clover, a scholarly demon who mostly uses their ability to tinker and hack, is the thief.
• Fire-Forged Friends: In the beginning, the three of them often clashed with each other - Ichika and Hiro just have incompatible personalities (plus the former never wanted to work with a team in the first place), while Clover is a demon whose Blue-and-Orange Morality makes them difficult to deal with at the best of times. As they fight together, though, they gradually grow to understand and trust each other. A few arcs in, both Ichika and Clover are fully committed to helping Hiro with his quest to find his mysterious saviour, even if they have to break a few laws in the process.
• Red Oni, Blue Oni: The impulsive and cheerful Hiro is the red oni to Ichika's calm and collected blue. Ironic, since Hiro has blue hair.

The Hero of the series. When he was seven years old, Hiro was possessed by a demon and would have died if not for the intervention of a mysterious Alcyon Corporation agent; ever since then, he's idolized the company and dreamed to join its ranks. He's cheerful and kindhearted, if a bit impulsive... and the persistent memory disorder he got from his brush with possession doesn't help matters.

His unique ability is Maxwell's Demon, a weapon-type mare that allows him to summon a sword. One edge behaves as a normal sword while the other absorbs any mist it cuts.

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• Amnesiac Hero: Downplayed. He got amnesia 11 years prior to the start of the story, but has recovered many of those memories since then and has a pretty good idea of who he is due to living in a future world with good record-keeping.
• Blue Is Heroic: He has blue hair and wears a lot of blue, and is the protagonist as well as one of the most heroic characters in the story.
• Big Eater: Has a tendency to order way too much food at cafes and restaurants, since he wants to try everything and has poor impulse control. His pockets are usually filled with snacks, too. Could be justified, since the other half of the time his memory problems make him Forget To Eat...
• Childhood Friends: With Nanami.
• Dragon Knight: He has this as a motif. Her demon form is dragon-like, and his mare gives him a knightly sword; when he achieves mantle, these combine into Twilit Knight, a super mode with aspects of both in the form of armor and wings.
• Duality Motif: His double-edged sword, mismatched eyes, and Orange/Blue Contrast all serve to foreshadow his status as a lucid changeling - a hybrid of human and demon. All subtlety goes out the window when he unlocks his mantle, Twilit Demon, which clads the left side of his body in armor.
• Electronic Eyes: He lost his left eye during the changeling invasion 11 years ago, and has a cybernetic replacement manufactured by Labyrinth. It has a few built-in apps, but otherwise is just a prosthetic replacement and doesn't confer any super senses. In fact, it becomes something of a problem when Alcyon Corporation comes into direct conflict with Labyrinth...
• Energy Absorption: His sword's Waking Edge can absorb mist and store it for later.
• Fake Memories: As part of his memory disorder, Hiro experiences a lot of confabulation, often remembering mundane events that didn't happen at all. It's implied that at least some of these are memories from his demon side, twisted by his brain to make sense within his human life.
• Following in Their Rescuer's Footsteps: He joined Alcyon Corporation to follow in the footsteps of the mysterious woman who exorcised him, and specifically wanted to join the defense division to do the same work as her (but was rejected).
• Forgetful Jones: Due to a past brush with possession, Hiro has a memory disorder that makes him this. His inability to remember Ichika's last name is a Running Gag.
• Heroes Prefer Swords: He's the heroic protagonist, and he has a weapon-type mare that manifests a knightly sword.
• Hybrid Power: It turns out that this is the reason Hiro has such enormous mist reserves: due to the botched exorcism that made him a lucid changeling, his current soul is made up of most of a human soul and most of a demon soul, making it nearly twice the size of the average soul. However, it's made clear that Hybrids Are a Crapshoot, and he just got lucky; other lucid changelings have ended up relatively normal or as Empty Shells.
• Instant Armor: His wake allows him to generate armor-like scales... but only in small patches, since he can only create them in places where he's been injured already. Twilit Demon plays it straighter, since it removes that restriction.
• The Knights Who Say "Squee!": Ever since he was rescued by an Alcyon Corporation agent at seven years old, Hiro has been a huge Alcorp fanboy. Even though he's part of the company now, he still tends to freak out and start babbling when he meets famous defense division agents.
• Merger of Souls: The present-day "Hiro" is actually the merged form of the original Hiro and the demon who possessed him. When he was incompletely exorcised at the last minute, some part of both their souls ended up inhabiting his body, mixed into a new soul.
• Minor Living Alone: He's 18 now, but he's been living alone since he was 16. His parents died when he was seven, and he lived with an aunt until he got an internship at Alcyon Corporation and moved out since he would feel bad imposing on her for any longer.
• Oblivious to Love: Poor Nanami. Hiro repeatedly fails to pick up her hints, believing she just wants to be his friend, even going as far as to invite Ichika along on some of their "dates"...
• The Pollyanna: Despite having been through a lot, Hiro remains unfailingly cheerful, and it's difficult to upset him for more than a few seconds. Other characters are usually a bit unsettled by the casual way he talks about his Dark and Troubled Past.
• Power Makes Your Hair Grow: When his mantle is active, his hair grows to about waist length.
• Recurring Dreams: He often dreams about himself as a child with the large, oarfish-like demon that possessed him (actually part of himself).
• Selective Obliviousness: As the series progresses, it becomes increasingly clear that a lot of Hiro's Idiot Hero tendencies are intentionally feigned so he doesn't have to confront uncomfortable truths. As more and more of Alcyon Corporation's corrupt dealings are brought to his attention, he finds it increasingly more difficult to ignore them, eventually leading to some forced Character Development.
• Spontaneous Weapon Creation: He can summon Maxwell's Demon out of thin air.
• Stock Shōnen Hero: He's a cheerful and determined young man, impulsive and a bit Book Dumb, and a Big Eater.
• Storm of Blades: Twilit Demon allows him to summon infinite copies of the Waking Blade. Naturally, he uses them as projectiles.
• Sword Beam: The energy absorbed by his sword can be released in a slash attack of this form.
• Team Chef: He lives alone, so he's gotten a lot of practice cooking. He sometimes gives food to his teammates as a way to show affection.
• Technicolor Blade: The two edges of his sword are bright cyan and orange respectively.
• Tomato in the Mirror: He's actually a lucid changeling - a human/demon hybrid created by a botched summoning. He's disturbed to realize that the seven-year-old "Hiro" whose life he's living is, in some ways, a different person entirely from the current him.
• Took a Level in Cheerfulness: According to Nanami, he used to be a shy and withdrawn kid who had trouble making friends. Apparently, the experience of almost dying in a changeling invasion made him determined to live his life to the fullest. It might also be the influence of his demon side's personality, since she's shown to be much more cheerful and outgoing from the beginning.
• Unskilled, but Strong: Hiro has a hard time learning complex theory and techniques, but his natural mist reserves are so enormous that he muscles through many early threats without trying too hard. This infuriates Ichika, who takes pride in her technique but still gets overshadowed by his pure strength.

The leader of Hiro's small team, who's working for Alcyon Corporation so their medical division can help her manage the symptoms of her natural mare. Despite not being very enthused by this arrangement, her competitive streak and perfectionism have led her to excel in the field anyway, recently breaking the record for fastest promotion to twilight rank in recent history. So when Hiro shows up and starts overshadowing her with his sheer power, she's a little peeved.

Her unique power is Hoarfrost, an elemental-type mare that allows her to create ice. As a natural mare, it has a few side-effects - mainly, her body temperature is always dangerously low, and she has to dress warmly and take medicine to keep herself functional.

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• Aloof Ally: Subverted. She likes to project the image of being one, but as Hiro points out, once you look past her harsh words, she's a considerate leader who spends a lot of her time helping her teammates out.
• Aloof Dark-Haired Girl: She's a relatively tall girl with dark hair and a cold and distant demeanor. She's described as handsome by a number of other characters, especially in the arcs where she's working in defense, where her coworkers wonder if she could work it into her image.
• Ambiguously Bi: Ichika's intense hero-worship toward her supervisor Misaki comes off as less-than-platonic at times, but when asked if she's romantically interested in Hiro, she responds no because he annoys her rather than any gender-based objection (although Hiro's Ambiguous Gender Identity may add another layer to this). With Oneirosea mostly being a No Hugging, No Kissing series, it's unlikely this will be resolved anytime soon.
• Career Not Taken: She wanted to be a lawyer, but then her mare manifested and derailed her entire carefully planned life. Now she's stuck at Alcyon Corporation slaying demons so they can manage her symptoms.
• Cloudcuckoolander's Minder: She serves this role to Clover (and sometimes Hiro), reining in their reckless behaviors and keeping them on-task.
• Consummate Professional: She's always serious, but she goes out of her way to project a professional air when she's actually on the job, and frequently expresses disdain for characters who don't do the same.
• Elemental Weapon: In a pinch, Ichika demonstrates the ability to create Wolverine Claws out of ice, though she normally prefers long-ranged combat.
• Flower Motifs: She has the character for "flower" in her first name, and her birthday is 8/9 (which can be read as hana, or flower). Several of her techniques and even her mantle reference flowers in their names. More specifically, she's associated with the plum blossom, a winter-blooming flower that symbolizes elegance and perseverance, and often drawn with them in official art.
• Friendship Denial: While Hiro considers Ichika his friend practically the moment they meet, Ichika takes much longer to come around. Even after she gives up on correcting him, she still generally refers to him as a subordinate or a teammate rather than a friend.
• Hidden Heart of Gold: She takes great lengths to cultivate an Aloof Ally persona, and becomes very annoyed when Hiro sees through her attempts.
• An Ice Person: Her mare, Hoarfrost, gives her the ability to create ice. Unusually, she cannot control the ice once it's created, and has to maintain contact with the ice or it disappears. This gives her a rather unusual hit-and-run fighting style.
• Last-Name Basis: In keeping with her overly serious image, she refers to basically everyone with last names and insists they do so for her as well. Hiro's inability to remember her last name is a point of conflict between them for quite a while before she gives up and accepts him calling her "Ichika-san".
• The Lancer: Although technically The Leader of their squad, the series' focus on Hiro's personal quest to find his mysterious savior means that Ichika's plot role is more like this trope. Her serious, pragmatic demeanor contrasts Hiro's cheerfulness and strong sense of justice. In later arcs, they cover each other's weaknesses and work together quite well.
• Locked Into Strangeness: Unlike other characters, her unusual black and white hair is not the result of biomodifications or dye, but a symptom that spontaneously manifested along with her mare.
• The Perfectionist: Ichika holds herself to incredibly high standards. Whenever things go wrong, her first reaction is always to wonder how she could have done better, even if it was due to completely unforeseen circumstances or the incompetence of others.
• Perpetual Frowner: Of the focused and serious subtype.
• Professional Voice Dissonance: Several arcs into the story, it turns out that the deep, accentless voice Ichika has been using this entire time is actually a professional voice she constructed so that people would take her more seriously - when she's talking to her parents, she slips into her natural Tohoku regional accent. She's NOT happy when Hiro finds out about this.
• Required Secondary Powers: Due to having manifested a mare through unpredictable natural means, Ichika actually lacks a required secondary power - namely, immunity to the cold temperatures her power generates. Worse, she has to maintain skin contact with the ice she generates, or it disappears. As a result, she has to use Hoarfrost carefully and sparingly in order to avoid giving herself frostbite.
• Stock Shōnen Rival: Gender-Inverted Trope. She's a dark-haired, cool and analytical demon slayer with more experience than Hiro, who only works with others because she can't go against the higher-ups' decisions. Although they're on the same team, they often butt heads over ideological differences, and consider each other to be their rivals.
• Surprisingly Normal Backstory: Ichika is loath to share any details about her background, insisting that it's irrelevant information and not professional to discuss. This, combined with her having a natural mare (which is associated with recurring nightmares), implies a Dark and Troubled Past. It's not until several arcs in that we discover that... she's an only child from a small town up north with loving and supportive parents who call her regularly. The natural mare thing happened purely because she stressed herself out with her academic perfectionism.
• Victory by Endurance: Her mantle, Killing Frost Garden, is built on this trope. Temperatures inside the garden steadily drop as time goes on, and since neither Ichika nor her opponent are immune to the cold, one of them will become unable to fight eventually. She describes it as a "test of endurance" to see who will drop first.

A diel (a demon with an android body provided by Alcyon Corporation in exchange for working at the company) who's just arrived in reality and is eager to learn everything they can about it. Mysteriously, they're the only person to recognize Hiro's description of his mysterious saviour, so he latches onto them immediately and they become fast friends... despite Clover's lack of common sense and general oddness.

Their unique power is Hijack, a manipulation-type wake that allows them to remotely control anything (or anyone) they stab with their tentacles, with improved strength and precision the more times they stab the same target.

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• Armed Legs: Clover can vent a pair of monstrous birdlike legs over their humanoid ones and use them to kick and gouge.
• Bad Powers, Good People: Their wake allows them to physically hijack and control other people, even using their abilities or cutting off their breathing. Still, they manage to be a well-meaning and mostly heroic character who fights more malicious demons.
• Blue-and-Orange Morality: Clover comes off as a bit of a Cloudcuckoolander because, being literally inhuman, their priorities just don't line up with their human teammates. Their first priority is to learn, and they accepted Alcyon Corporation's deal just so they could get into reality and learn about it... but unlike human scholars, they're just as eager to learn strange or pointless information like "how will people react if I start screaming at them" or "how does it feel to get an arm chopped off" as complicated scientific topics. They even look forward to experiencing death, and are only concerned about dying in that if it happens too soon then they won't get to learn anything else.
• Born Winner: All diels are said to be this, but it's especially evident with Clover since we get to watch their progression alongside their human teammates. In short, diels have an intuitive grasp of the basic mist-manipulation powers and don't need to train to use them; even as a sunlight-rank rookie, Clover demonstrates a savage and incredibly effective fighting style. Despite being their supervisor, Ichika is more focused on reining them in rather than teaching them to be more effective. As the plot goes on, though, the other side of this trope shows itself: Clover's knowledge of their abilities is so instinctual that they have trouble consciously training and improving, and they eventually struggle to catch up to their human teammates.
• Combat Pragmatist: Clover fights pretty dirty, primarily because they have very little idea of what humans consider to be "fair". They're perfectly willing to feign weakness, go for the eyes, or attack enemies while they're distracted.
• Curious as a Monkey: Clover's curiosity manifests as an impulsive and childish streak - they're always poking their nose into anything and everything, and the question they most often test is "what would happen if I did this?".
• Cute Little Fangs: Their lower canines are pointed, giving them a cute but wild look.
• Electric Jellyfish: They're a jellyfish-like demon, and while they can't directly produce electricity, their tentacles are similar to wires and they're heavily associated with machines.
• Extremity Extremist: When not using their wake, they have a kick-heavy close-combat style. In fact, they rarely use their arms for much at all, possibly because their demon true form doesn't have any.
• The Gadfly: They're interested in seeing how humans react to different stimuli, so they'll often say strange or frustrating things mid-conversation just to see what happens. Their teammates know they don't mean any harm, and try not to hold it against them.
• Hacker Cave: They've transformed their company-assigned tiny cube apartment into one of these, filled with stacks upon stacks of old computer parts.
• Mythical Motifs: They're somewhat themed after gorgons, as a reference to the fact that adult jellyfish are called medusae. Their demon form has their tentacles positioned around their head like a gorgon's snake mane, and their face resembles some old Greek Gorgoneia. Their body shape and birdlike feet are also reminiscent of a cockatrice, another mythical creature with a petrifying gaze.
• Only One Name: It's just Clover. In fact, even that is just a nickname from some random researcher which stuck; they seem pretty apathetic about names in general.
• Perpetual Smiler: Their expression is almost always frozen in a wide-eyed cat smile, even during serious situations. It tends to unsettle people.
• Playful Hacker: Clover loves messing with machines, including hacking. Later on, they manage to figure out how to jailbreak their own robot body.
• Poisonous Person: They can make their tentacles and monster legs poisonous to the touch at will.
• Psycho Pink: They're well-meaning, but often come off as reckless or cruel due to their lack of human common sense, so their bright magenta hair evokes this trope.
• Triple Shifter: Being a diel, they don't have to sleep... so Alcyon Corporation gives them 12-hour shifts. They have to work with two separate teams, because their human teammates don't get as many shifts as they do.