Table manners in our opinion are very important to show your respect to others and the food as well as the environment for the meal. This applies to both Western and Eastern food cultures. If you don't practice suitable table manners during daily or casual life, it will be very difficult to behave properly when the challenges come. It is so common nowadays for you to hang out with friends from Japan or Asia overall. When you go to an authentic Asian restaurant, especially Japanese restaurant, you would like to show your respect to your friend and their home cultures. There are also more frequent business occasions that can happen with guests from the East. You definitely don't want to lose face or be offensive in front of your customers or suppliers. Thus, we highly encourage everyone to learn at least the basic table manners for both western and eastern countries.
There are common rules on the table for example, dos and don'ts for using chopsticks for all Asian countries including Japan, China, Korea, etc. Basic instructions can be found in this video by Tsunagu Japan . The unique thing in Japan is during most meals, chopsticks are the only utensils for eating. You don't see Japanese use spoons a lot, while forks and knives are for sure from western culture. Japanese people usually drink the soup directly from the bowls so the size of soup bowl is small and fitting to the hand to help. Also, you always want to put your chopsticks on its rest if you are not using them.
Except for some common rules above, in Japanese culture, people start and finish enjoying a meal by expressing appreciation. At the beginning of the meal, people say いただきます = Itadakimasu, which literally means I am going to start and at the end, you will hear ごちそうさま = Gochisousama, which literally means thanks for the nice meal. This is to appreciate the people who prepare the meal and all the animals/plants that are sacrificed for our appetite.
For more guidance on table manners in Japan, check out Rachel and Jun's video below. Never sitting on the table, enjoying your sushi with the proper way and trying not to make a mess at your table. Be careful and cautious, a little bit self-awareness and discipline can carry you a long way with better understand of the culture, more respect to the others and still enjoy the meal comfortably.