Place the unpeeled potatoes in large pot and cover them with about 1 inch of salted water.
Bring the water to a gentle boil and let the potatoes cook for 15-25 minutes, until fork tender. They may take a little more or less time depending on their size.
Drain the potatoes and let them cool completely.
Once cooled, chop the potatoes into bite-sized pieces and place them in a large mixing bowl.
Add the Kewpie mayonnaise, chives, salt, and pepper, and mix gently until well combined. Taste and adjust for seasonings if desired. You can add more Kewpie mayonnaise if you like it extra creamy.
Refrigerate the potato salad for at least 30 minutes (to allow the flavors to meld) before serving cold.