The player of the game takes on the role of Ico, a young boy born with a pair of horns, who must escort a princess named Yorda safely out of a castle without her being captured by the shadowy figures that prowl the castle or being killed by the castle's numerous environmental hazards. Despite selling only 650,000 copies worldwide, Ico received strong reviews, and has become a cult hit among video game enthusiasts.

Ico is noted for its highly individual artistic style. Key factors contributing to the game's absorbing atmosphere include the absence of any HUD; a bleak and washed-out use of color; low key use of in-game music, played only in selected scenes of the game; and atmospheric, ambient sound effects in the background. It makes effective use of minimal dialogue and story to forge strong emotional connections with the characters and environments in the game. It includes action, adventure and puzzle elements. The game also has a notable fictional language which has been theorized to be backwards Japanese.