In Japan, there is a proverb "good manners even between friends." This proverb means that "we should not forget courtesy with words and communication despite how close we are with each other." It is a communication of the Japanese people to be careful not to take a disrespectful attitude unconsciously even for families and friends.
First of all, greetings are important. In the morning, say "Good morning!"; from 11 o'clock lunch time until the sunset in the evening, say "Hello!" At night, say "Good evening!". Even the shy Japanese let go their tensions and cautiousness and you will be able to have a friendly relationship with them. It is also a characteristic of Japanese greetings to bow, not only with words, but with a smile (lightly lowering the head, bowing).
Next, it is the sense of distance between each other that we must pay attention to in communication with the Japanese. Questions of privacy, such as "How old are you?" "Are you dating anyone?" "Are you married?" "Do you have children?" are things Japanese people do not like so much. Especially as soon as we meet, there is an unspoken rule that makes it a very rude act to ask such a question suddenly of a woman who is not yet so close in a relationship. Also, keep in mind that acts such as approaching and touching the body (physical contact) must also be made with considerable caution.
"Excuse me" is one of the expressions I often use in Japan. Originally it is an expression of apology, but it is used in various scenes, so if you remember it, it will be of your help in various scenes. Japanese people say, "Excuse me!" when placing orders at restaurants, etc., or when calling out clerks at shops. Even when you want to ask questions to passers-by about your destination, the route to it, the way to go there, etc., it is natural to say "Excuse me." Even when you want to take a commemorative photo against the background of sightseeing spots, temples and shrines, beautiful natural scenery, etc., please hand over your smartphone or compact camera and ask "Excuse me, could you take a photo?". Of course, when you thought "I bothered you" or "Did I put you in trouble?", you can apologize with "Excuse me." It is a polite version of "sorry," and can be used even when you want to express the feeling that "Do you mind my asking?" "Please excuse me a moment" ... ... Japanese "Excuse me" has many different meanings.