Thanks rcstig C Hing, yes I got the same manual in English. However, my G6P charger is displaying in Japanese, which makes me everytime counter checking the English manual in order to find out which charging/discharging function I should be using....
I emailed G-Force and asked about the language setting. Indeed it can be changed to English as follow:
1. Download the latest English firmware from the office website
2. Connect the G6P charger to the PC by using a micro-USB cable, switch on the G6P, allow the PC to search for driver. This may take few minutes.
3. Once the driver is installed, execute the firmware. Then click update. Done.
I succesfully changed the menu language from Japanese to English.