There's all of I think two HK games so far, Wii Sports Resort and Wii Fit Plus.
HK version will be PAL and 240v. Japan version will be NTSC and 100v.
For the HK version in Japan you will need a TV that supports PAL, possibly a new one, a new power brick, and some form of mod to run Japan games, noting that crossing TV systems usually doesn't work too well with the Wii. The Japan model is popular here because you can run US games on it, European PAL games are often more expensive and require modification to operate.
Basically first check the TV where it's going to run to see if it supports PAL, next bring the console to SSP and ask for help getting it to run Japanese games and channels. Many games are TV system, region, and now country locked.