I never thought Potato Salad was very common for Japanese cuisine until searching recipes. Here is what is stated with the recipe I posted here, from Japanese Cooking 101 : "What makes Japanese potato salad Japanese? … the secret is in mayonnaise. To make ‘Japanese’ Potato Salad, you have to use Japanese mayonnaise. That is the key ingredient. Japanese mayonnaise tastes more tangy and salty, and is very different from American mayonnaise."
1Peel potatoes and cut into small pieces. Heat water in a pot, and boil potatoes until tender, about 10-15 minutes. Strain and put potatoes in a large bowl. Add 1/2 tsp salt and vinegar, and mash slightly (leave some potato chunks). Let it cool.
2Slice cucumbers to thin rounds, and cut carrots thinly (2" long). In a different bowl, sprinkle a little salt (not in the measurement) over cucumber and carrots, and let it sit for 2-3 minutes. Squeeze out water.
3Cut boiled eggs into small pieces, and cut ham thinly (2" long strips).
4Add vegetables, eggs, and ham to potatoes, then mayonnaise. Mix well. Add salt and pepper to taste.