Originally Posted by gudugan

You need a predeparture test only if you don't have 3 shots. Specifically you do NOT need 3 shots to enter, you just need a negative test. (Same as any other country).
After you land, they do a test on arrival to 20% of people. If you test positive, they send you an email and you are supposed to isolate at home.
btw, the wording on the site mentions "China (excluding Hong Kong and Macau)". Taiwan is also not counted as China here. Source: flew from Taiwan to Japan before rule change and did not need predeparture test/test on arrival