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.
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.
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.
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.
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.