The structure of the egg was once seen as analogous to the structure of the cosmos.
According to this theory, the eggshell was supposed to be the sky, the membrane inside the sky with clouds, the egg white symbolized water, and the egg yolk symbolized earth and minerals.
Until 1923, sushi was primarily served as street food.
After the 1923 earthquake that struck Japan, owning a restaurant became more accessible due to a rapid drop in property prices, and such estates gained popularity.