Asuma Sarutobi is the leader of Team 10 and son of the Third Hokage. He had a falling out with his father when he was younger, and briefly left Konohagakure in protest. The two had not completely reconciled by the time of the Third's death. Asuma is usually seen smoking a cigarette, but will temporarily drop the habit when something is bothering him, such as when his father died. [wikipedia]
