The Japanese are quite wary of tattoos and don't really like them. In Japan they are normally associated with gang membership and there are certainly plenty of gyms etc which will not allow entry with any type of tattoo that is visible. All that having been said, a tattoo is certainly not a medical ban and there are a few pilots that I know in both AJX and Jetstar Japan that have them. Without exception, however, none of these tattoos are visible when the pilots wear short-sleeved shirts.
So, my assessment of the AJX view is that if they can't be seen when you're in uniform then they don't seem to mind.
I know nothing about China's take on the matter.