I'm not 100% sure but i think these may have been the orig IOD fuse slot (Install On Delivery fuses). I think Mitsubishi had a male fused plug that fitted/plugged into this yellow box, it was then removed after final assembly until delivery, so that the battery is not depleted while the vehicle is in storage/transit, on delivery this plug was removed and the other fuses you see were installed.
These fuses should power radio, central locking, interior lights, which are the goodies in your car that need things that need constant power source (radio memory, central lock commands, interior lighting etc) hence the need to isolate them while in storage/transit to prevent a flat/depleted battery.
Like riggers and Maleficus said move the yellow box back and forth to get it to remove it from the relay box. Once the holder is out, you should be able to use needle nose pliers to remove the fuses from the holder, inspect and replace.
You can put it back if you want to, up to you, but its not needed.
Like i said, not 100% sure as i could be wrong?