The man is known as sir, or director. He is the one that had taken care of young-jin for almost all of his life on the island. Back a few chapters ago, sir threatened to kill young-jin and dispose of him while he was under the effects of the poison. Sir "knight in shinning armor:" Seung-houn came to the rescue to save young-jin. After making sir a peice of worthless sh*t, he let him go sparing his life. When sir here states that seung-hyun is supposed to protect him, sir means that he shouldn't be harming him anymore and that he should leave him alone as said. Hope this helps! 