According to official statistics for 2019, the number of Japanese travelers increased by 11.0% to 3,271,700 for South Korea, by 10.1% to 2,167,900 for Taiwan, but decreased by 16.2% to 1,078,800 for Hong Kong on a year-on-year basis. 

Japanese travelers to South Korea resulted in year-on-year growths for two years in a row, while those to Hong Kong reduced for the first time in the last six years. 

The graph below shows the yearly changes in the three destinations in the last decade (China has not disclosed the results since 2016):

For December 2019 only, Japanese travelers decreased by by 59.6% for Hong Kong due to the political turmoil. South Korea decreased those by 1.2% to 255,300, but Taiwan stably increased those by 12.6% to 225,300. 

The graph below shows the monthly changes in the three destinations in 2019:

In Japanese