Are all non-Jewish/Christian/Muslim people kafirs?

Is everyone who is not either Jewish or Christian (dhimmis) or Muslim kafirs? I assumed that was the case, but Wikipedia says > The term refers to a person who rejects or disbelieves in the god of > Islam or who hides, denies, or pays no attention to the Islamic > version of truth. and the section Types of disbelief seems to be describing scenarios where Islam is offered to someone, and they reject it. Would someone who has had never had Islam promoted to them by another person still be a kafir? For example, would someone living in North Korea be a kafir, or a Japanese person who believes in Buddhism and Shinto be regarded as a kafir?