|“||They tried to sacrifice me because I have horns.||”|
–Ico, after releasing Yorda from her cage
Ico (イコ Iko, pronounced "ee-co") is the young protagonist of the game named after him.
Ico is the latest victim of a mysterious curse, manifested in two large horns growing from his head. Any misfortune that befalls Ico's home village is blamed on him, dooming him to a life of alienation. On his twelfth birthday, a handful of horsemen take him in shackles to a mysterious castle and place him in a coffin to starve, hoping his immurement will rid the village of trouble.
A tremor, however, shakes Ico's coffin from its ledge; his casket breaks open on the floor, freeing him but knocking him out momentarily. While unconscious, Ico experiences a vision of a spiked cage overflowing with a dark shadowy energy. When he awakens and explores the castle, he quickly finds his vision to be much more than a dream. Inside the cage is Yorda, an ethereal and delicate young girl, trapped by her mother in the cage. Ico presently frees her, alerting the minions of the castle to rise from the floors to recapture Yorda. When Ico fights the creatures off, and when Yorda uses her abilities to open the way forward, it quickly becomes apparent that the two need to work together if they want to escape their prison.The Queen and her minions thwart Ico's progress, and eventually Ico becomes separated from Yorda just as freedom seems certain. Ico is forced back into the bowels of the castle, eventually gaining a mysterious sword that will allow him to open the Idol Gates that only Yorda could open previously. In a final confrontation with the Queen herself, Ico manages to overcome the Queen's defenses and kill her with the sword; he brutally loses both his horns during and after the fight, blacking out as the castle comes apart around him.
He wakes up on a boat that has found its way to a beach. Walking down the shoreline, he discovers Yorda and the pair are reunited.
Ico originally looked quite different and played a different role in the castle than he did in the final game. Earlier revisions of the game had him as a servant in the castle, which was apparently occupied by normal humans. At this time Ico himself was an ordinary boy, instead it was Yorda who bore the horns. During the course of Ico's duties he came across the imprisoned princess, and decided to try to free her.
Ico acquired the horns for gameplay reasons: when testing the game it was found to be too difficult to tell which character you were controlling, so the horns were added to Ico to make him stand out more. It was only after he was given the horns for gameplay reasons that the story was rewritten to include them as a significant element of both his character and the story as a whole.