To change the brightness on the F-07C, you must  go to Control Panel

and click the brightness setting which is in Japanese. (very last choice, last row second column)

It says:

Brightness Settings

[Set the brightness by yourself(Manually)]

[Have Windows set it automatically]

Just check set the brightness by yourself. If you let windows choose, the light sensor (the bulbous thing next to the charge / msg light that turns different colors) will auto shift the brightness to whatever the light is like in your room.