Be open minded especially with food.
Stay on one side of the escalator to make way as a passing lane.
Let everyone off the train/elevator before entering.
Be mindful that trash cans in Japan are extremely rare. Only public trash is the public toilet such as train stations.
Try and learn some basic phrases such as “thank you” or “hello.”
Hide your tattoos if you can. Long sleeves and pants are highly encouraged especially at public spots such as gym or even restaurants.

TIP. Tipping is not mandatory/forced as it is in States. Tipping is only in US/Canada.
Talk loudly or make phone calls in public places such as trains, cafes, etc.
No eating/drinking while walking or on public transport. Even if it’s a cup of coffee or boba. Bullet train is the exception.
Jaywalk. This applies mostly at busy main streets however small neighborhoods is fine.
Wear gym clothes or revealing attire.
Smoke in public spaces. You can only smoke in designated areas that is labeled.
PDA. It generally is frowned upon to show affection publicly. No matter how drunk you are.
Open/close cab doors. The cab driver will do it.