Came across your post while doing some searching so thought I would finally join up
I also have a Fuga which is in Japanese.
1: Press the TV/Aux button.
2: Press the left button in the centre of the big rotary knob. The AUX setting in the bottom left will go yellow like this:
3: Press the centre button in the rotary knob. It will then come up with this menu:
4: If AUX is yellow, press the centre button again! If not, spin the rotary knob until it is yellow.
5: Enjoy listening to music from aux source!