Originally Posted by Wuxia

If you need to clear immigration at PVG, the transit time allowed at PVG airport is now 72 hours as long as your passport is one of the 45 nationalities listed (Japan included). If not, better ask China Eastern where you clear immigration and what type of visa you need. There is also a chance that you might not need to get off the plane at PVG and will clear immigration in Kunming, in which case, it's surely less than 24 hours.