If a man (China nationality) marries a woman (Japanese nationality), what will happen to their nationality?

First of all, it has nothing to do with men and women. It depends on which country you are in. For example, if you are in China, you used to be from China, now you are from China, and you used to be Japanese. It depends on your position in Japan. If the marriage is recognized by the Immigration Bureau, you immediately have the' permanent residency' in Canada, but your nationality is still Japan. If she is already a "permanent resident" in China, whether you are married or not, your status will not be improved. You still have to live for a certain number of years, pass the "Naturalization Examination" of the Immigration Bureau, take an examination of Canadian history, geography and some simple laws and regulations, and prove that you have integrated into Canadian society and can become a qualified Canadian citizen. At this time, your nationality will change.