Cause and Effect, Urashima Taro and the Princess of the Sea.

Urashima Taro opened the box that the Princess of the Sea told him that he shouldn't open, because if he did, he would never be able to see her again.

Cause

Effect

The effect was that Urashima Taro returned back to his real age, 324 years old. Since he broke the princess's rule, he was never allowed back to the palace, and he died.