I manage to show the sprite by set camera z-position to higher value than 'main character'.
Is this the right way? Since it's not mentioned in tutorial.
Yep, that should fix it! I had assumed you were having a different issue when I posted, but I'm glad you got it figured out :D
The tutorial mentions the coordinates you should use for your sprite actor and camera actor, doesn't it? Do we need to make it clearer somehow?