Tokyo is exactly 1 hour ahead of Hong Kong year-round. When it's 3:00 PM in Tokyo, it's 2:00 PM in Hong Kong. Neither Japan nor Hong Kong observes daylight saving time, so this difference is constant.
The small time difference makes business coordination between Japan and Hong Kong very convenient.
Any business hours work great! With only a 1-hour difference, 9:00 AM - 6:00 PM Tokyo corresponds to 8:00 AM - 5:00 PM Hong Kong. Full business day overlap.
Tokyo and Hong Kong are connected by numerous daily flights (about 4 hours), making same-day business trips possible. Both are major Asian financial centers.