but, I think Japan is off topic for comparison since it's not even a Christian nation.
Japan's irreligiosity is also massively overstated relative to actual quotidian life in the country, even by Japanese people. I've said on this site in the past that Japan is probably one of the only 'low religious identification, high religious observance' societies on Earth. It's certainly the most extreme example that comes to mind.
Despite over 60 years of so-called athiest government, I also find that China is definitely more religiously devout than anywhere in the western world, save the southern US. Though overt discussion of faith will elicit laughter.