Potato salad is eaten all around the world and popular in Japan. However it is consider not as side dish but as snacks or tapas served at izakaya tavern. Also potato salad is sold at supermarket in plastic boxes.
Another way to eat potato salad is a sandwich. Probably no other country in world eat potato salad sandwich.
The ingredients except potato are carrot, cucumber, corn, onion, ham, tuna, boiled egg, mandarin and apple.