Don’t reach over to press elevator buttons
Most Japanese elevators don’t have staff waiting in them to push the buttons. Instead, you’ll have to do it on your own. Or, if you’re in a packed elevator, you should ask the person standing nearest the control panel to press your floor’s button.
Reaching over and pressing the button yourself is super-rude. Not only do you have to wiggle around to create space for yourself, but you also need to stick your dirty finger in front of someone who has the easiest access to the control panel. If you can’t communicate in Japanese, you can say it English. Maybe someone will understand you.