In the end, I decided to keep the quest details hidden. I do know that Lyon is a trustworthy person but since this quest is a secret. I need to keep it that way... unless Lyon was able to discover it himself or the guild master told him about it.
"I don't know much about the detail of the quest Lyon, all that I know was Ligh need someone to help her protect the supplies caravan until it reaches its destination..." I said that.
"I feel like you're not being honest with me here but I think I know why you can't tell me more about it. So I wouldn't ask about it anymore." Lyon said.
Thank god that Lyon was able to understand it. Well, he's a former adventurer and considered to be one of the strongest, at least that is what I heard from the talk around the adventurer guild before. So Lyon might have done a quest that required him not to tell anybody about it as well.
Creation is hard, cheer me up!