Name: Uchiha Sasuke
Age: 13
Birthday: 23 July
Zodiac: Cancer
Rank: Genin
From: Leaf
Teacher: Kakashi
Teammates: Uzumaki Naruto, Haruno Sakura
Family: Uchiha Itachi (elder brother)
Favourite technique: Grand Fireball Technique
Background: Sole survivor of the Uchiha clan when his elder brother went on a killing rampage.
The Deal with him: Sasuke was a regular ninja student with big dreams of being an excellent ninja like his elder brother. But after Itachi killed their family and screwed up his mind to "live in an unsightly way", Sasuke became cool, and calls himself an 'avenger', whose purpose in life was to kill his brother. For some obscure reason, that made all the girls at the academy fall in love with him.
Sasuke first started to use his Sharingan when he fought against Haku with Naruto at Wave Country. His eyes and body attracted the liking of Orochimaru, who wishes to take over his body after he became truly strong. To show his admiration, Orochimaru left a cursed seal after delightfully sinking his fangs into Sasuke's neck, which Kakashi sealed, but threatens to unleash everytime Sasuke gets excited in a fight.
After engaging in a precarious fight with Naruto, Sasuke felt inferior as he seemed not to be improving as much as Naruto. Orochimaru took the chance to send the Sound 4 ninjas to convince Sasuke to leave the Leaf village to seek more power from Orochimaru. Thus, Sasuke abandoned Konoha (Sakura's endless whining might have helped him decide to leave in a hurry) and is on his way to the Sound village.