Will you be arrested if you fly the Chinese flag in Japan? And if you fly the Japanese flag in China, is it considered a traitor?

As long as you abide by the laws of other countries/home countries when flying the national flag, there will be no arrests.

In China, things related to Japan and Japanese people can also fly the Japanese flag, such as international hotels, Japanese-owned enterprises, international exhibitions/sports games, etc.

There is no crime of "traitor" in domestic law, so there is no such thing as a traitor legally.

Han traitor is a traditional and subjective view and definition among the people. Its meaning, implication, and standards are different in different environments, contexts, and positions. In other words, the same behavior may or may not be considered a traitor by some people.