You have to be fast , but its not hard at all. I discovered this after completing Hsu Haos mission for finding him work. After you talk to him he gives you 500 sapphire koins. and when he runs and tries to disappear bump into him then before he can recover talk to him again and he will give you 500 koins. and you can do this over and over again as long as you dont let him disappear. If you've already done this mission theni gu ess you'll have to start another Konquest. im not sure if this is the only mission you an do this with, but i guess any mission where the char runs away to disappear after giving you a reward it will work.