Please be aware that Tokyo has multiple airports and that these results are for all airports serving the city.
The best month to fly between Tokyo and Hong Kong is September and the most expensive month to fly is February. (Average prices, based on 893 datapoints.)
The best day to arrive at Tokyo is Thursday and it would be best to avoid Saturday, as prices are on average 67.94% higher than on Thursday. (Average prices, based on 644 datapoints.)
The cheapest airline flying from Tokyo to Hong Kong is Hong Kong Express. They are 86% cheaper than Air Japan. (Average prices, based on 915 datapoints.)
The best time to fly is at around 2. (Average prices, based on 1190 datapoints.)