Here is a recipe for Japanese Egg Salad Sandwich, Tamago Sando. I made this today and it was good. I used Japanese Mayo KEWPI and I also recommend using white milk bread and cut off the crust has shown here. The step you may want to skip is the making of pickles, simply use prepared relish or buttered pickles which can be easily bought. I also use one tea spoon of Dijon Mustard mixing it with the KEWPI Mayo and I do not use salt at all.
It is important to measure the cooking time for the eggs carefully. Tamago Sando is easy to make and delicious. Enjoy!