The instructions were in Japanese, but I think we got them figured out (after a little trial and error).
First you boil your eggs. My method is to cover eggs in cool water and then heat them to boiling on the stove. Once the water is bubbling, let the eggs boil for 3 minutes. After the 3 minutes, turn off the heat, cover the eggs, and let them sit.
After about two hours, while the egg is still warm, we took of the shell and placed it in the egg mold. After closing up the mold, it is important to put the egg and mold into cold water or the refrigerator. We found that if we did not do this, the egg held it’s new shape for only a few minutes. However, if the egg cools in the mold, the egg holds it’s shape for the next day’s lunch box.