Voiced by: Junko Minagawa
- Abusive Parents: His mother is constantly having a mental break down and hurting him in the process. His father hardly seems to care, spending more and more time at work in order not to deal with the situation at home. Seimei was the one who actually did the looking after Ritsuka, while their father only intervenes to whenever his wife's behavior starts to annoy him.
- Big Brother Worship: Played completely straight.
- Can't Stand Him, Can't Live Without Him: His relationship with Soubi.
- Cat Boy
- Defrosting Ice Queen: He warms up to Soubi a lot compared to how he was when the two met.
- Even the Guys Want Him
- New Transfer Student: At the beginning of the story.
- One Head Taller: The reverse and exception, played straight (without the humor).
- Pointless Band-Aid: Frequently has a bandaid on his face, and though it looks like this trope at first, it's not.
- Silly Rabbit, Idealism Is for Kids!: Implied upon with his "missing" personality and his current one.
- Stepford Smiler: He smiles often to show that there are no problems to people outside his house.
- Tell Me About My Brother: Subverted and played straight. He does have his memories of Seimei, but he is constantly asking about him for one reason or another.
- Troubled, but Cute: And his counterpart is indeed Soubi.
- Tsundere: Especially around Soubi.
- The Unchosen One
- Wise Beyond Their Years: He known for reading very complex books for a hobby.
Voiced by: Katsuyuki Konishi
- Berserk Button: Doesn't like being reminded of his "training" with Ritsu. Nisei's mere existence also qualifies as well.
- Broken Bird
- Combat Sadomasochist: He insists to be dominated by Ritsuka. Though he was raised to be like that.
- Defiled Forever: Thanks a lot, Ritsu.
- Even the Guys Want Him: Ritsuka, Seimei, Ritsu, Kio...
- Extreme Doormat: Not surprising, given his background.
- Friendless Background: Kio notices.
- The Glasses Come Off: Whenever he starts a battle.
- No Name Given: In-universe, he actually does not has a name, such as Beloved and Loveless, he is a blank Fighter that can be assigned to any Sacrifice.
- Not So Stoic: Shown with a few examples, but most notably when he meets Seimei again for the first time during the present storyline.
- One Head Taller: Though certainly more than a head taller than Ritsuka, he often gives him comforting hugs. Sometimes inverted with Ritsuka, though not for humor.
- Parental Abandonment: His parents died when he was only six years old in an accident.
- Rape as Backstory Though not his entire background, it's still a rather important part of it.
- Sins of Our Fathers: Ritsu abused him because his mother married another man. Yeah, Ritsu's a jerk.
- Stepford Smiler: Extreme Type B.
- Unstoppable Rage: Even if Ritsuka hadn't ordered him to fight Nisei, he probably would have found an excuse to fight him anyway.
Voiced by: Ken Narita
- Authority Equals Asskicking: Heavily implied.
- The Bad Guy Wins: In volume eight.
- Beauty is Bad: Very bad. He has even been described as having beautiful ears and a beautiful tail.
- Beware the Superman
- Big Bad
- The Cowl
- The Dreaded
- Hero Killer So very much.
- Manipulative Bastard: Lampshaded a few times, most notably by Youji, during the attack on the school.
- Faking the Dead
- Identification by Dental Records: How his body was ID'd. Subverted, like whoa.
- Posthumous Character: Subverted big time.
- Purity Sue: He's described as perfect and loving in all the flashbacks seen of him. Thoroughly subverted once he shows up again in the story, but he tried to show up like that to his brother.
- Shrouded in Myth
- Slasher Smile
- Walking Spoiler: He is very much alive, and is the Big Bad.
- Yandere: For Ritsuka, he is willing to kill, rape and wreak havoc, even if it's not what Ritsuka wanted.
- Beauty is Bad
- Blessed with Suck: Namely when your destined partner doesn't really give a crap about you unless it's convenient for him.
- Break the Cutie: He tries. Though he doesn't get one hundred percent of the wanted results, he's at least somewhat successful.
- Don't You Dare Pity Me!: Inverted. He wants to be pitied. He would probably think a get-out-of-jail-free card would have been nice, too. He was quite upset to not having been shown any sympathy.
- Enigmatic Minion
- Evil Counterpart: He's similar to one for Soubi, as they are both Seimei's Fighters.
- For the Evulz: It's just another way of having fun.
- Manipulative Bastard
- Nothing Can Stop Us Now!: Until he realizes he actually can't win in his fight against Soubi and Ritsuka.
- Psychopathic Manchild: Love could go die in a ditch and he'd still be happy.
- Slasher Smile
- This Means War!: He is certainly not on good terms with Soubi.
Voiced by: Kana Ueda
- Extreme Doormat
- Huge Schoolgirl: And how!
- Love You and Everybody
- Plucky Girl
- Shipper on Deck: For Ritsuka and Soubi. (Though a good number of the fans hate her regardless, simply because of her Matchmaker Crush on Ritsuka.)
- Wise Beyond Their Years: Noticeably averted. She is the only 12 year old of the main cast who actually acts like a 12 year old, with the naiveté and innocence of one. This tends to clash a little with the Zeroes (male) and Ritsuka, who all act far more mature, and adds to her Ron the Death Eater treatment and the label "stupid" (There's never evidence that she is, she's just the only one who acts their age!). Ritsuka himself later admits that she's not actually stupid, and in fact he seems to envy her.
Voiced by: Jun Fukuyama
Voiced by: Ken Takeuchi
Voiced by: Wakana Yamazaki
- Abusive Parents: She was shown to have been unstable before Seimei's death, but that was what really pushed her over the edge.
- Freudian Excuse: It's implied that she was abused herself, not that it excuses her behavior.
- The Ophelia: A very unstable and violent version.
- You Should Have Died Instead: To Ritsuka, among the many other abuses she heaps on him.
Voiced by: Mamiko Noto
- Christmas Cake: Deconstructed. Not only is she unmarried, but also a virgin... and it shows since she still has her cat ears. Her self-esteem takes a nosedive because of this. Though technically she's not Christmas Cake, since she's only 23.
- Psychologist Teacher: She tries.
- Shrinking Violet
- Artificial Human
- Bad Liar: Youji is one, apparently because he thinks it's pointless. When Natsuo skips school he has to come up with an excuse and fails miserably. Even Yuiko almost caught on. Contrast to Natsuo's Consummate Liar.
- Creepy Twins: By their actions. They aren't actual twins.
- Consummate Liar: Natsuo is stated to be one by Youji. Apparently he always keeps a straight face and even Youji can't tell when he is or isn't lying. This contrasts nicely with Youji who couldn't tell a lie to save his life.
- Don't You Dare Pity Me!: Something of Natsuo's initial reaction to Soubi's kindness before Soubi outright asked Natsuo (and Youji) to live with him.
- Eye Scream: When Natsuo was little, he accidentally put his right eye out.
- Feel No Pain: Or temperature, as Soubi realizes...
- New Transfer Students: In chapter 85.
- Jerks With Hearts Of Gold: They really can be the nicest people one could ever meet - especially Natsuo. Not that this stops them from being blunt, rude, or sarcastic when they feel like being such.
- Never Tell Me the Odds: When they head out to confront Seimei, Nagisa tells them they'll be murdered because they aren't strong enough. They go anyway (and with Ritsu's approval), and not only do they come back alive, but if Ritsuka hadn't burst into the library when he did, they probably would have gotten somewhere, considering Seimei reacted to Natsuo saying he would control his name.
- Replacement Goldfish: Youji, for Nagisa's sister.
- Took a Level in Badass: Natsuo.
- Turn Coat
- Artificial Human
- Catgirls: Before they lose their ears to each other.
- Driven to Suicide: Subverted at the last minute.
- Feel No Pain: Initially for Yamato.
- Friendly Enemy: Yamato meets Ritsuka for lunch and inadvertently reveals that she can feel pain.
- Schoolgirl Lesbians
- Screw Destiny: Their ultimate decision.
Voiced by: Sanae Kobayashi
- Womanchild: Lampshaded by Youji, who says that you'd never guess she's over 30.
- Elegant Gothic Lolita
- Moral Dissonance: She knows that Ritsu raped Soubi when the latter was a child, and while she's disgusted by it she hates Soubi for it. Most likely due to the fact that she's in love with Ritsu.
- The Unfavorite: Exhibited by her towards Sacrifices; she absolutely hates Sacrifices. The only exception to this rule being Youji who looks like her dead little sister.
Voiced by: Takehito Koyasu
- Bespectacled Bastard Boyfriend: To Soubi
- Depraved Bisexual: Debatable. He loved Soubi's mother and was furious when she married another man, and seemed to have no problem sexually abusing Soubi in her place. Like many real life child sexual abusers, his abuse of Soubi had more to do with control than actual physical attraction, since he says "Be dominated" to Soubi, before his usual routine of hitting Soubi with a whip under the guise of "training." While it seems while he wanted control and power over Soubi, there are hints lying around that he does genuinely care for him. That training may have been both to protect him and to have power over him.
- Eye Scream
- Manipulative Bastard: Soubi at least seems to believe he's this.
- Nice Hat: His character in Wisdom Resurrection wears one, then a new one later on.
- Noble Demon: He's done horrible things. That isn't going to stop him from trying to pick a fight with someone who has done worse horrible things. He also can't stand Seimei for having wronged Soubi. In fact, it comes out as more of a personal grudge, but he can't stand the fact that Seimei "completely ruined Soubi". Not to say this excuses his past behavior nor some of his present behavior, but he's not entirely all that bad.
- Ritsu: You can't get angry if you don't care deeply.
- Not in This for Your Revolution
Voiced by: Aya Hisakawa