Avocado is not indigenous to Japan. As it was introduced relatively recently, some Japanese still don’t like it. But it quickly became popular when someone found out that it goes very well with soy sauce. The fatty texture of the fruit resembles fatty tuna. Even in the United States, California rolls include sliced avocado.
Avocado rice bowl is easy and great for vegans. You can use either seasoned rice for sushi, or unflavored cooked rice. Slice 1/2 avocado and place on top of the bed of rice in a bowl. Top with thinly sliced nori and wasabi if you like. Drop a small amount of soy sauce just before eating.