Teito is the protagonist of the story.
He has a sad past that never will leave him quiet for the rest of the life. He was marked as "sklave" (slave) when he was just a baby, and he hasn't memories of the past.
His first memory is the death of his father, because of Ayanami's hand. He meets him ten years later the assassination of the father and in that moment he looses the control, trying to hit an official commander.
This episode marked Teito's fate because he's been arrested and in order to help him to escape, Mikage, his best friend, is captured by Ayanami, that subjucating him with his power, made him the strongest opponent for Teito. Now he's forced to fight against him and in order to save Teito, Mikage chooses to lose his life, that previously remained in Ayanami's hands.
He manipuled him and after another meeting with Teito, Mikage is constrincted to fight against him. This episode causes the awakening of Mikhael, the God that lives in the Eye of Mikhael, the jem that Teito hides in his hand. And Mikage dies, reborning in a little dragon called Burupya.

The meeting with Frau, Castor and Labrador helps Teito to become stronger, and especially Frau, is a sort of father for him. The most important person that becomes a guide and a reference point. Teito is full of sadness but he can look to the future thinking to fight for Mikage's sake.
The exam in order to become bishop is the moment of the begin for him. He can believe in the others thanks to Mikage and Frau's words, and day by day, he becomes stronger.
Teito is smart, strong and quiet. He lives doesn't care of the thoughts of the others, he's just himself.
His eyes are sad and he doesn't speak too much. He's unfriendy with the others, the most important thing is to hide his pain (and his name, beacuse he can't revail his real identity of prince of Raggs). Many times he can appear aggressive and overconfident, but his aggressiveness is a sort of "barrier" that he uses in order to don't be hurted.
This is an aspect of his personality that I love very much, because his mind is very difficult to understand. He's a reflective person, that always make his decisions thinking very well to the consequences that they could have to the others.
But he can be sweet... and with the development of the story he'll have the chance to show all the love that his heart hides since he was a baby that needed an embrace.
I die everytime he hugs Capella, they're very sweet, ABSOLUTELY sweet!!!
That baby shows him the meaning of love, and Teito became more "human", more gentle and protective. Not only for Mikage's sake, but for Capella's sake, Frau's, Hakuren's sake... now he smiles more than before, because he understood how is important not just for yourself but for all the person you love.
Mikage always had a smile for all, especially for him. So now he has a cute and sincere smile for Capella. Teito needs Capella more than Capella needs him, he's the place where Teito's heart can be opened without blessing again.
Sometimes Teito is inpulsive and he can hit who tries to hurt his friend, he's a very special person! After the recovereing of his lost memories, Teito decided to become the successor of raggs Realm and disperately search for all the truth, hides behind Ayanami and the Seven Ghosts Legend.
When Mikhael influences him, Teito doesn't lose the control, and Mikhael can feel his feelings and respects them, because he considers Teito his "master", the choose to be The King.
Teito's heart bleeds, yes... and the power of Mikhael makes him a sort of schizophrenic, because another existence lives into him. When Teito looses the control for some strong reason, Mikhael take his place in Teit's mind and reveals his existence. His eyes become red like blood and the expression become evil and sarcastic.
He's located in the " Eye of Mikhael ", a jem that Teito's father hides in one his hand when he was a baby. The power of Mikhael is the one thet only the successor of Raggs Kingdom can hides in his body, and since that moment Mikhael was sealed like in an eternal dream.
Mikage's death awakes him and now Teito is afraid to lose the control and kills someone, because his death instinct isn't something he can controls. And it doesn't concerns just Ayanami, but to every situations and persons. He becomes powerful and his evilness obfuscates his mind. It's thanks to Frau and his friends if he's able to remain himself... for now.

The positive thing is that Mikhael can feel Teito's feeling and for this reason he respects them, loving who he loves and hating who he hates.
An example is the thanksful that Mikhael gives to Hakuren to be friend of Teito, or the desire of killing Ayanami, that he possesses since the murdered of Teito's father.

In a funny drama CD Mikhael drinks Frau's saké and takes the control of Teito's body. Acting consequentially... he makes all crazy, especially Frau and Hakuren! XD His personality is strong and very child, he's a god and everyone near to him try to makes him happy even if he desires stupid things! XD