
Tae-Ha was not born a slave. Rather, he chose to swear an oath to defend the Crown Prince, thus he endured the loss of his command, the torture, the permanent branding of slave symbol on his forehead, because he had a greater purpose.
Slaves who ran away were rounded up by bounty hunters called chuno-kkun. “Chuno” itself is a portmanteau word combining “chase” with “slave”; hence, slave hunter.
In the Manchu war, amidst the chaos and fighting, invaders had raided homes and dragged off their inhabitants.
Chun Ji-Ho is nothing if not an opportunist. He tells his men to fire away. If he manages to kill Dae-Gil and the runaway slave, that's like killing two birds with a few dozen arrows.