Ikai no Kifujin ga Shounen wo Kifujin ni Sodateru wo Hanashi

A slave boy who had been so abused that his eyes were empty was on his way in a rickety carriage to clean a chimney, a very dangerous job that eventually choked the lungs of those small children who performed it. Suddenly, an elegant carriage blocked their path. A beautiful lady exited and took the boy away. Why was the slaver calling after the lady's carriage, warning the boy not to go?