from Wikipedia - http://en.wikipedia.org/wiki/Nabari_no_ou
Rokujo Miharu (六条 壬晴)
The protagonist of the series, Rokujo is a 14-year-old middle school student. He holds Nabari's hijutsu, the Shinrabanshō, in his body. He pretends to act indifferent to those around him in order to protect them from getting hurt, though he is not averse to acting in a rather innocent and cute way in order to get what he wants. Though seemingly apathetic, he does have feelings and is sensitive to those around him. He cares for animals, such as his cat Shiratama. He remembers little of his childhood, and had lost his parents at a young age. His only goal is to inherit his family's okonomiyaki store.
Kumohira Thobari Durandal (雲平・帷・デュランダル)
Rokujo's and Kouichi's 25-year-old teacher in the "front world". Born in Ireland on March 17, Kumohira is actually a ninja of the Banten village in the world of Nabari. He is entirely devoted to protecting Rokujo, and wants him to become the ruler of Nabari. He has an intense hatred of transport, such as trains and buses, and would not get on one until Rokujo manages to "persuade" him. He went to Japan because his grandfather was a "Japan otaku" and "ninja fanatic", who forced him to go to learn to become a ninja, and was unable to return home for ten years (partly due to his phobia of vehicles). In the anime, he is the temporary leader as the current leader is away, while in the manga, he is not just a stand-in, but actually has the power to arrange for a temporary leader. According to Aizawa, Kumohira has probably recorded Banten's kinjutsu through verbal communication.
Aizawa Kouichi (相澤 虹一)
Rokujo's 14-year-old classmate who studies nindō under Kumohira. Though he normally has an energetic attitude when around others, he is serious and relentless when it comes to his ninja duties, and is apparently fascinated with death. It is later revealed that his love of death is a result of his own inability to die. His immortality is attributed to the holder of the Shinrabanshō during the Edo Period, who was a medical practitioner, experimenting with placing the wisdom of the Shinrabanshō into animals, since humans usually died. There were only two survivors of the experiments, both of whom gained immortality as a result. Kōichi's ultimate goal is to find a way to die, as well as ensure that "monsters [like himself] are never created again."
Shimizu Raimei (清水 雷鳴)
Raimei is a 14-year-old guardian of the world of Nabari, and the head of the Shimizu clan. She is also a Fūma-nin (風魔の忍 Fūma no nin, "Wind Magic/Demon Ninja") who prefers fighting with a sword (named Kurogamon (黒我聞)) over using ninjutsu, claiming to be a samurai. She has the tendency to mistake one person for another, or reveal information she means to keep to herself, when excited. Five years ago, her older brother, Raikō, annihilated their clan, and she has sworn to kill him in revenge.
A 16-year-old ninja in the Kairōshū who uses the forbidden technique "kira". This technique shoots the user's ki into the body of a target and controls it from the inside out, which can cause the target's bones to break or their body to completely explode. The cost of using this technique is the loss of the user's life force, gradually losing their five senses and eventually dying. According to volume 4, he has roughly two more months to live. In anime version, he has a few months to live.
He slowly begins to form a bond with Miharu after a promise that the two made to each other. He will protect Miharu to gain what he wants. Although, in the beginning he tells Miharu that he will kill Miharu's friends if the promise is not fulfilled. That promise was, by using the Shinrabanshou, Miharu would erase Yoite. Later, Yoite reveals that he does not actually want to die, and wonders if he ever truly was alive. In chapter 47, Yoite tells Miharu that he never actually put his ki into any of Miharu's friends. He just said that so Miharu would do what he wants. It is also revealed in 47 that Yoite is neither male or female.
Yoite was even shorter, and more fragile than Miharu before the side effect of kira starts, which makes Yoite grew into maturity in just 3 days. It was mentioned that Yoite was covered with blood when Hattori Tojūrō took him back to Kairōshū. Hattori knew the secret of Yoite and persuade Miharu not to fulfill his desire. At the end of the chapter Miharu and Yoite betrayed Kairōshū and escaped to Banten village.
Yoite's real name has finally been revealed in chapter 46. His real name is Koudou Sora (香道そら). He seems to have a younger brother named Koudou Tsukasa. Assuming that they're actually related, Yoite's full name may be Koudou Sora. It is also said that his parents abandoned him when he was a child and he hasn't seen them since then.
Yoite visited the church three times a month, sitting alone on the last row of the church just gazing at the light from the window. Kids never went near him nor hurt him. This lasted for three years until two years ago, when Tsukasa took him away from the town. Yoite hasn't come back since then.
copied from Wikipedia - http://en.wikipedia.org/wiki/List_of_Nabari_no_Ō_characters
from the top, clockwise: Yoite, Kumohira Thobari Durandal, Rokujo Miharu, Shimizu Raimei, Aizawa Kouichi.
some of the seiyuu of Nabari no Ou are quite well-known too...
Rokujo Miharu - Rie Kugimiya
Kumohira thobari Durandal - Daisuke Namikawa
Aizawa Kouichi - Satoshi Hino
Raimei Shimizu - Ayumi Fujimura
Yoite - Mitsuki Saiga
Fuma Kotaro - Ryotaro Okiayu
Saraba - Akeno Watanabe
Juji Minami - Kimiko Koyama
Tojuro Hattori - Joji Nakata
Ichiki - Yuri Amano
Kazuhiko Yukimi - Kenjiro Tsuda
Raiko Shimizu - Junichi Suwabe
Gau Meguro - Nobuhiko Okamoto
Yae Oda - Satsuki Yukino
Soro Kato- Tetsuya Kakihara
okay, there's this undeniable similarity between Nabari no Ou and Naruto... the Shinrabanshou in Miharu is similar to Naruto's Kyuubi no Kitsune which everybody wants it in order to be the most powerful one... PLUS, Raimei's brother, Raiko, killed everyone of the Shimizu clan just like Sasuke and Itachi.
i myself also think that it is quite similar to other animes. the appearance of Miharu is quite similar with Lelouch from Code Geass (and also ALMOST as cold-hearted as him). The Shinrabanshou in Miharu seems to have a female soul or something like that which reminds me of C.C. in Code Geass. Raimei looks alike with Sawachika Eri from School Rumble. And that Fuma Kotaro's role and characteristics in Nabari no Ou is exactly like Urahara Kisuke from Bleach. Kumohira's fear of transport is like Natsu's motion sickness in Fairy Tail...
@.@ and a whole lot of other similarities.
But i really like the opening song...=3
Miharu have a poor taste of fashion...XD
He's a devil.
And he acts cute...=.=
Miharu and Yoite
Kumohira trying his best to avoid transport with the reason that lumps of steel are unreliable...XD
if i were to rate this anime, it'll be a 4 over 5...