The man had seen his comrades get slaughtered and didn't resist when YuWon began asking questions. Apart from the one YuWon killed first, the rest weren't ogres or onis, as the man told him.
These people had dressed as onis, evolved forms of ogres, but in reality, were slaves of the actual oni. The oni had been expelled from his clan and grabbed the few people he could, enslaving them and dressing them up as onis.
In the end, they became a glorified con group, fooling humans and enslaving them. Not only that, but they also sold some slaves to the actual oni that ruled this part of the forest.
YuWon realized that if they frequently sold slaves, then it was probable that Lysandra had also been taken there. In that case, only the man could guide him there.
"Where do you sell the people at?" YuWon asked.
"In the cave up north! I can take you there—"
"How many people are there?"