Foreshadowing in "Urashima Taro and the Princess of the Sea"

The foreshadowing in "Urashima Taro and The Princess of The Sea" takes place when the princess gives Urashima the jewel box. She says, "There is just one thing about that box, you must never, never open it if you ever wish to return to the Palace of the Sea." This foreshadows that Urashima will open the box, and he will have to face harsh consequences. It includes this information to show that he will indeed open the box, and he will not be allowed back into the Palace of the Sea.