The combat in Ico is focused on protecting Yorda from the shadow creatures which pursue her. If Yorda is captured and subsequently pulled into one of the portals from which the shadows emerge, it is game over. The puzzles generally involve finding or creating a route that allows her to traverse an area, so that she can open the gates at the exit, allowing both to proceed forwards.
StoryEditYorda is imprisoned in the cage by her mother, the Queen, who intends to use her as a spiritual vessel. The Queen's own body is dying, so she will continue to live by taking Yorda's. After Ico succeeds in freeing Yorda from the cage and leading her to the main gates of the castle, the Queen appears before them. She tells Ico that Yorda is her daughter, and reminds Yorda that she cannot survive in the outside world. At this point the Queen withdraws, and the pair continue trying to escape.
When they are finally on the verge of freedom, the Queen appears once again, this time petrifying Yorda. Ico returns to the tower where he was to be sacrificed and faces the Queen. She states that Yorda cannot leave no matter what, and tells him to leave. Instead Ico fights the Queen, and manages to kill her. Yorda is brought back to life, still herself in mind, but in body she has become the shadowy form seen in Ico's dream. In this form she seems more assertive and is significantly physically stronger. She quickly figures out what has happened, and as the castle crumbles around them, she carries the unconscious Ico down to the dock and releases him to the waters beyond. However, Yorda herself stays behind in the collapsing castle.
After the credits are finished there is a scene in which Ico, under the player's control, finds Yorda washed up on the beach; she has returned to her white, human form, but now with color blooming on her once-pale cheeks.