I starting driving in Japan two months ago.
I have been a driver in other countries for more than 25 years so I am not a novice driver however I find driving in Japan quite stressful.
Driving on the left side of the road, all the car controls on the opposite side than I am used to, the narrow roads, road signs that I can't read and the use of road mirrors (which I am not in the habit of doing) and parking in tight spots.
For me, the hardest thing is avoiding bicycles. I am not used to bicycle riders riding on the sidewalk and suddenly popping out in front of me.
Just drive slowly and deliberately. My driving instructor told me that everybody breaks traffic laws but the key is to do it slowly so that everybody can SEE you doing it and avoid you.