A young man who loves girls with glasses, is half-Yomu, and is thus immortal. His mother is a busy Spirit World Warrior, and is often away from home. He meets Mirai when simply walking outside of her school and seeing her standing on the edge of the roof. Unaware of her powers, he mistakenly assumes that she's about to commit suicide. Their relationship begins with Mirai constantly attacking him as practice, but blossoms into a close friendship after he accompanies her on ventures to kill violent Yomu. Akihito is actually the host for an immensely powerful Yomu known as Beyond the Boundary or Kyokai no Kanata.
Amazingly Embarrassing Parents: His mother is introduced in a holographic post-card message, in which she is wearing a skimpy cat-themed costume, using every Japanese cat-related pun possible. On career day, she dressed up in a panda suit and pretended to be one of the students.
In episode 8, Akihito's mother appears again in another holographic post card. This time she's wearing a very Stipperiffic hamster outfit while talking like a Valley Girl. Akihito actually went into a semi-Heroic BSOD out of embarrassment.
Brought Down to Normal: When he had the Beyond the Boundary removed for 3 months, he lacked his immortality and was able to control his youmu side. Snapped back after he returns the Beyond the Boundary to being inside him.
Butt Monkey: Seems to be heading in that direction. Mirai uses him as a practice dummy, Mitsuki labels him a pervert and teases him, Hiroomi gives him weird nicknames...this guy doesn't get much respect.
Non-Action Guy: Despite hanging out with Spirit World Warriors, he doesn't have any combat skills. Until he gets an Eleventh Hour Superpower in Episode 12 and can partially control his youmu side at least.
Playing with Fire: Appears to be his main method of attack when possessed by the Kyoukai no Kanata.
Person of Mass Destruction: When the Kyoukai No Kanata is in control, he's strong enough that it takes 3 people to contain him, and even that wasn't enough in episode 4. One stray ball of fire caused a humongous explosion several kilometers away and he created a gigantic crater around the site of his containment.
Took a Level in Badass: Episode 12, as he has part of the Kyoukai no Kanata in his hand he has access to some of it powers. He later reseals the Youmu inside of him again.
Superpowered Evil Side: After another youmu possesses him, the Kyoukai No Kanata takes over temporarily, turning him into a fireball-spewing rage monster. This apparently happens regularly, and his handlers may have to kill him if they can't contain his crazy-mode.
A young girl who is descended from a clan of Spirit World Warriors who are capable of manipulating their blood and turning it into weapons. Since this power was highly feared and envied, her clan was wiped out, and she was eventually the only remaining member. She was temporarily taken in by the Inami Clan, but they apparently ousted her after she killed one of their members when attempting to free said member from possession by a powerful Yomu. At first she constantly attacks Akihito because of his immortality, thus making him a good means of training, but becomes close friends with him after he agrees to help her fight normal Yomu. After she killed Yui Inami, the Inami family was dead set on having her killed, but she was saved by the Nase clan who planned on using her to kill Akihito, who hosted an immensely powerful Yomu. Her first attempts at attacking him were not her using him for practice, but actual attempts at learning the extent of his power in order to eventually kill him. However, when she finally got the chance, she had already fallen in love with him and instead chose to sacrifice herself. While she doesn't die, she's absorbed by the Beyond the Boundary and must defeat it from within.
A-Cup Angst: Not brought up much, but it's clear that Mirai is somewhat sensitive about her small bust.
Accidental Murder: She accidentally killed her friend Yui Inami when the latter was possessed by the Hollow Shadow.
Action Girl: For an inexperienced Spirit Warrior, Mirai can kick ass like no one's business.
Character Tic: Turning her back on the camera and tapping on her phone, apparently blogging while asking rhetorical questions. It's usually only used as a gag though.
Cool Down Hug: Glomps Akihito, stopping his fiery rampage and allowing him to regain consciousness.
Crouching Moron, Hidden Badass: In the initial episodes, Mirai is presented as too clumsy and inept to really be considered a threat. However, after she gets over her angst over killing Yui Inami, she suddenly starts kicking all sorts of ass.
Cry Cute: When she was lost, and again after she calms down Youmu-Akihito.
Dark and Troubled Past: When she was a child, Mirai was adopted by the Inami family. She was kept isolated in the attic, but was befriended by Yui, a member of the Inami family. Mirai and Yui were close friends until the day that the Hollow Shadow swept into town. Mirai and Yui were caught in its wake, leading to Yui getting possessed. Mirai accidentally killed Yui while trying to fight off the Hollow Shadow.
Fantastic Racism: Played for laughs. Akihito complains about being stabbed multiple times over the week by Mirai. She protests that since Akihito can't die from the wounds, he has nothing to lose. Akihito retorts that he can still feel pain and that picking on him is discrimination.
Meganekko: One of the foremost things Akihito finds attractive about her.
Not So Different: From Akihito. At first, Mirai rejects Akihito's attempts at sympathizing with her, arguing that Akihito couldn't possibly understand. After Mirai witnesses Akihito's Super-Powered Evil Side in action, she realizes that he really did understand what she was going through.
Overdrawn at the Blood Bank: Rule of Cool applies, but she still frequently uses several times the amount of blood a human body contains within a single fight. Deconstructed after Episode 10; she used so much blood attacking the Beyond the Boundary that she doesn't exist anymore.
Mitsuki is the youngest daughter of the Nase clan, a wealthy and powerful clan of Spirit Warriors, and shares the family power of creating cages, primarily defensive shields. She also uses a rodent-like youmu familiar in combat. Mitsuki is the president of the Literature Club and friends with Akihito; evidently this means she's constantly teasing him. However, underneath her initial unapproachable exterior is a Lonely Rich Kid who would very much like to have friends.
Familiar: Uses a rodent-like familiar to combat youmu.
Lonely Rich Kid: Izumi tells her in a flashback that as Spirit Warriors, they're always going to be alone, moreso for Mitsuki as she's a daughter of the powerful Nase clan. She isn't shown to have plenty of friends outside the main cast.
Not So Stoic: She often tries to hide her emotions, but is sometimes not very good at it like when Mirai convinces her to go to the festival.
The Ojou: She comes from a well-known and very rich Spirit Warrior family, although she doesn't act in a particularly haughty or refined way.
Pet the Dog: Despite telling Akihito to avoid further contact with Mirai, Mitsuki treats Mirai nicely. Mitsuki helps the other girl find Ayaka's shop when the latter got lost and offered Mirai the gemstone after killing a youmu.
Hiroomi is the middle child of the Nase clan and Mitsuki's older brother. Much to her dismay, this also means he claims to have a sister complex, and much of his interactions with his sister result in her reprimanding him for his behavior. (They really do love each other, though). He's also friends with Akihito, with whom he gets along spectacularly.Hiroomi shares his family's cage-erecting powers. He also fights with his scarf, which is enchanted to erase parts of the user's body.
Ambiguously Gay: Towards Akihito of all people. He has total and complete disregard of his personal space, insists on calling him by an embarrassing nickname, and seems to be the only one who constantly worries about the others wellbeing. There is also a lingering look or two and an Out-of-Character Moment.
Badass: Someone who can use a barrier to block the Hollow Shadow while simultaneously fending off dozens of youmu deserves this title.
Barrier Warrior: Creates a huge barrier to block the Hollow Shadow while simultaneously fending off numerous smaller youmu. In fact, barriers appear to be his specialty.
Makes a barrier to contain Akihito after his Super-Powered Evil Side takes over. He is ultimately unable to maintain the barrier under Akihito's assault.
Birds of a Feather: He and Akihito. Hiroomi's quirks aside, they are very, very much alike. They generally act like they practice their interactions with each other.
Nino-san actually calls them out on it in episode 7.
Nino-san: You two get along far better than I expected.
Bishōnen: So far the greatest example on the show.
Broken Pedestal: Spent his life wanting to be like his older sister Izumi. In Episode 12, he acknowledges that he has to move past this, because the same episode reveals Izumi harbors a shade in her body herself.
Childhood Friends: With Akihito. Although it's implied that Hiroomi and Mitsuki are less "friends" and more "guardians" to make sure Akihito's youmu side doesn't go berserk.
Covered with Scars: He's got some serious scars on his back. Episodes 4 and 5 reveal that Akihito did this to him after having lost control of his Youmu side.
The Gadfly: He enjoys teasing Akihito way too much and actively creates situations that make him uncomfortable.
Incest Subtext: One-sided and played for laughs. He openly admits that he has a sister complex and enjoys reading literature that involve little sisters. His sister, on the other hand, does not appreciate Hiroomi's sentiments.
He tones it down about the time the shows halfway point rolls around and it looks more like he has more of a Big Brother Instinct than a sis-con.
Mr. Fanservice: Bishounen, had a shirtless scene. Heck in the third Idol Saiban ova, he is naked except for his scarf. And the animators made sure we had a good look. They even played up the Ho Yay he had with Akihito to Akihito's displeasure.
The Nicknamer: Hiroomi gives Akihito the nickname Akkey, to the latter's displeasure. According to Akihito, it makes him sound like a washed-up pop star.
Nice Job Breaking It, Hero: In order to see if his sisters' goals are as benign as they seem, he sneaks into the family vault and does some investigating... And forgets to lock the door behind him. This gives Miroku the opportunity he needs to steal the Hollow Shadow's Yomu Stone and feed its power to his staff.
Scarf of Asskicking: He actually uses it in battle. And he has more than one. We have seen four as of episode 7. He wears them because his powers as a Spirit World Warrior make him extremely sensitive even to the slightest cold.
Improbable Weapon User: They work by erasing parts of the target's body. Justified, since they're probably magic.
Spirit World Warriors
Voiced by: Hiromi Konno
Akihito's eccentric mother, who's also a busy Spirit World Warrior and thus constantly away.
Very Punchable Man: Her demeanor tends to annoy people so much that they want to kick her.
Wacky Parent, Serious Child: The Wacky Parent to Akihito's Serious Child, what with her always embarrassing him with her childish antics and revealing outfits.
Voiced by: Moe Toyota
A member of the Inami family who has very little spiritual power, and must rely on a special weapon to fight Yomu rather than her own power. She can't remember who exactly gave it to her, only that she could only keep it under the stipulation that she kills Mirai. Her weapon becomes more powerful as she feeds it yomu stones, but nearly devours her as well. She's saved by Mirai and reconciles with her afterwards.
Foil: To Mirai, who is more emotional and has a stronger Sixth Sense. Solidified in their interactions after Sakura moves in with her.
I Just Want to Be Badass: Sakura has weak Spirit Warrior powers, unlike her sister Yui and Mirai. In an attempt to strengthen herself, she made a deal with Miroku. She would borrow a weapon that would increase in strength as it is fed youmu stones in exchange for killing Mirai.
New Transfer Student: She transferred into Mirai's class so she could have more opportunities to kill her.
Nice Job Breaking It, Hero: Akihito was possessed by the Hollow Shadow. Mirai would have been able to fight it without him getting involved if not for her pointless pursuit of murdering Mirai. Instead, Mirai was forced to stab him and spray him in her blood. Akihito's youmu instincts kicked and it wasn't pretty.
Cast From Hitpoints: Her weapon becomes progressively more powerful as it's fed youmu stones, but requires more and more energy from its wielder. Eventually, the weapon will consume its wielder if the user can't supply it with enough energy.
Roaring Rampage of Revenge: Averted. Initially, it appeared Sakura is trying to avenge her sister Yui by killing Mirai, but really Sakura was trying to kill Mirai as part of a deal she made with Miroku.
An Interrogation Officer in the Spirit World Warriors Society who comes to visit the Nase family in order to monitor the Hollow Shadow. He was the one who gave Sakura her weapon, knowing that it would devour her. He apparently needed it to become stronger, and he also has plans for Akihito.
He takes on Ayaka in her youmu form with minimal difficulty. Note that Ayaka is considered extremely powerful, on par with warriors of the Spirit Warrior Society. However, he fought her during the Calm, where Ayaka's powers were significantly weakened.
Expy: Of Yuuki Terumi. He's a Soft Spoken Sadist who works for a seemingly benevolent organisation with a goal that revolves around obtaining an incredibly powerful force For the Evulz, who even happens to use attacks similar to Terumi's (however whereas Terumi uses snake chains, Miroku uses worm-like energy blasts). Luckily he's not a tenth as unpleasant as Terumi.
For the Evulz: Even after he loses his chance at obtaining Beyond the Boundary, he still goes out of his way to amplify its power in order to lessen Mirai's chances of defeating it from within and hinder everyone else's efforts to help her, simply because it "suits someone like him."
I Surrender, Suckers: Upon being defeated by Izumi and knowing that his plan can no longer succeed, he proceeds to blow himself up in a massive explosion.
Jerk Ass: He's callous, is not above murder, and is willing to do things that could potentially end the world seemingly For the Evulz.
Bitch in Sheep's Clothing: She'd been planning Akihito's murder since before the first episode. She was the one who sent Hiroomi to "subdue" him, which resulted in the scars on his back.
Combat Pragmatist: She's been planning Akihito's murder for a very long time now because he's the host of the powerful Beyond the Boundary. This is primarily because the Society of Spirit World Warriors is also after him. She planned to have Mirai do all of the dirty work.
Easily Forgiven: She gets off pretty much scott-free after arranging Akihito's assassination and then convincing Mirai to sacrifice herself in order to achieve her ultimate goal of destroying the Beyond the Boundary—which, by the way, did not work. Justified in that her actions make a lot of sense when you look at things from a pure logical standpoint, and she's clearly not ecstatic about the job either.
Flash Step: One of many techniques she utilizes in combat.
I Did What I Had to Do: Her motivations for trying to kill Akihito had nothing to do with him, but everything to do with how it was the only way to defeat the Beyond the Boundary, a youmu capable of destroying the world that he was hosting. She's not exactly excited about this part of her job.
Nice Job Breaking It, Hero: Remember how Akihito lost control of his youmu side and attacked Hiroomi? She was the one who told Hiroomi to do something that would set off his Youmu side in the first place. The incident nearly got her little brother killed and left Akihito severely traumatized.
Obviously Evil: She's stoic, reserved, elegant, distant to her little sister, focuses a lot on reputation, and stole the Hollow Shadow from Mirai. But subverted when it turns out she's actually the closest thing to a Big Good shown in the series yet.
Ayaka makes a business out of appraising youmu and paying Spirit World warriors for the crystals youmu leave behind. She's also one herself, but prefers her kimono-sporting, humanoid form over her kitsune one.
Badass: We see how powerful she is in the last episode, able to destroy at least dozens of average Youmu with a single Breath Attack
Barrier Warrior: Is also capable of setting up barriers like the Nase clan. When she and Hiroomi team up in Episode 4, it's her job to repair the cage Hiroomi keeps up.
A very powerful youmu whose power distorts the space around it, resulting in the world gaining a purple tint and its outward appearance as a huge shadow, earning it its name. This youmu was what caused Mirai to kill Yui when it possessed her.
Attack Its Weakpoint: What you have to do to actually bring the fight into more even ground in the first place, then again to finally kill it.
The Worf Effect: For such a massive and powerful youmu, it went down rather quickly. The methods required to defeat it directly cause the emergence of Beyond the Boundary in Akihito again.
You Cannot Grasp the True Form: The huge shadow is actually the result of space being distorted around the actual youmu because of how powerful it is. Once the youmu is sufficiently weakened by Mirai, the shadow disappears and it's true form is revealed.
Beyond the Boundary / Kyoukai no Kanata
A youmu of inconceivable powers. Born of the negative feelings of countless humans, this massive entity has the power to destroy the world with ease. Since before the show, it had been sealed inside of Akihito for an unknown amount of time, emerging whenever his human consciousness grew weak due to extreme amounts of physical damage. This youmu's mere presence was also responsible for Akihito being Nigh Invulnerable.Due to how dangerous it is, Izumi had conspired to have Mirai kill Akihito, and through him, the youmu, before people like Miroku could somehow use it for their own ends. It is extracted from Akihito by Mirai at the end of episode 9, and remains as such for three months, before Akihito absorbs it back into his body again near the end of the final episode.
Anti-Magic: On numerous ocassions it has shown the ability to negate the powers of spirit warriors, including Mirai's blood, even during the Calm.
Demonic Possession: This was Akihito's so-called "youmu side". Therefore, every time it appeared it took over was an instance of this trope.
Genre Savvy: It knows it becomes weaker during the Calm, so rather than stay and raze everything to the ground, it actually retreats when confronted in order to wait out the Calm.
Hell Is That Noise: A loud, booming sound that only Akihito can hear, presumably due to having harbored it.
Nigh Invulnerable: The only thing that could supposedly kill it was the blood of the Kuriyama clan. And while it was said blood that was capable of extracting it from Akihito, what stopped it in the end was being absorbed back into Akihito.
Reality Warper: Hoo boy. Whenever it manifests, strange phenonema abound. The ground becomes reflective, like looking upon a lake, and gains a strange tint. Youmu grow very active. When it was freed from Akihito, it created a new dimension and stayed there to save itself from death, then began to absorb the powers of spirit hunters and youmu alike in order to sustain itself. Its insisdes feature an almost exact copy of whatever it is reflecting, and it can be basically anywhere in it at once to attack.
You Cannot Grasp the True Form: The closest thing it had to this (and what it defaults to, really) was Akihito's appearance. Without that, it's basically a gigantic reflective surface.
Walking Spoiler: The significance of this being to the story is ridiculous.
The Worf Effect: Not even it is unaffected by the Calm. To note, it was weakened enough to the point of actually becoming killable, although Mirai elected to remove it from Akihito in favor of killing him along with the youmu.