I'm going to China for work (a conference) for about a week, and thought it may be nice to visit my friend in Japan for 2-3 days or so on the way back, especially with the reduced flight costs compared to flying to Japan from the US at a later time. I've found a few references on difficulties flying to China from Japan in certain circumstances (e.g. the site referenced in this question), but not the other way. I'm concerned because I've heard about these issues from Japan->China as well as knowing Chinese nationals require a Visa to enter Japan, and while that doesn't apply to me, I don't know if there will be mixups at the airport because of that state of affairs, or if there's special procedure/law I'm not aware of.
This would all be pre-planned, no open ended tickets, so USA->China (~1 week)->Japan (a few days)->USA would all be pre-planned if I did this. Are there any known difficulties with this sort of travel plan? I'd prefer not to be stuck in China figuring out how to get tickets back to the US ASAP because I can't do my preplanned flight path.