Cause: Because the old man answered the last question correctly...
(Come again spring)

Effect: As a result the Princess of the Sea rewarded him by letting him stay at a beautiful palace, and letting him live forever.

Cause: Since Urashima saved the tortoise from death...

Effect: Death disappeared and did not bother the old man anymore.

Effect: But instead growing old and dying because of his disobedience of opening the box.

Cause: Urashima opened the box, hoping to find a way back to the princess...

Cause

and

EFFECT