Directed by Fumito Ueda, who wanted to make a "boy meets girl" concept, the game revolves around a boy named Ico, Ico was born with horns (which his village considers a bad omen). Warriors lock him away in an abandoned fortress. However, due to him pushing stone coffin around, he was able to escape. During his explorations of the fortress, Ico encounters Yorda, the daughter of the castle's Queen. The Queen plans to use Yorda's body to extend her own lifespan. Learning this, Ico seeks to escape the castle with Yorda, keeping her safe from the shadow-like creatures that attempt to draw her back. Throughout the game, the player controls Ico as he explores the castle, solves puzzles and assists Yorda across obstacles.
Ico introduced several design and technical elements, including a story told with minimal dialog, bloom lighting and key frame animation, that have influenced subsequent games.
Although not a commercial success, it was critically acclaimed for its art and story elements and received several awards, including "Game of the Year" nominations and three Game Devlopers Choice Awards. Ico is listed on several overall top game lists, and is often considered a work of art. The game was reprinted in Europe in 2006, in conjunction with the release of Shadow of the Colossus, the spiritual succesor to Ico. Along with Shadow of the Colossus, Ico was released in The Ico & Shadow of the Colossus Collection for the PlayStation 3 which featured high-definition graphics and 3D support. This HD version was released separately as a retail version in Japan.
The game's protagonist, Ico, is a young boy with a pair of horns growing on his head—considered a bad omen by his village. As part of the village's tradition, he is taken by a group of warriors to a castle surrounded by water, and locked inside one of the stone coffins in a crypt. As the warriors depart, a tremor runs through the castle, collapsing the ceiling of the room where Ico is imprisoned; Ico takes advantage of this to escape his sarcophagus. As he searches the castle, he comes across Yorda, a captive girl who speaks in a language different from his. Ico helps Yorda escape, but finds she is hunted by shadow-like creatures (the souls of other horned children sacrificed to the fortress) that attempt to drag her into the portals from which they emerge. Although Ico cannot be harmed by the shadows and is able to drive them away from Yorda, he finds he cannot defeat the enemies with his simple weapons and can only temporarily drive them away. The pair make their way through the abandoned castle, eventually arriving at the bridge leading to land. As they cross, the Queen, ruler of the fortress and Yorda's mother, appears and tells Yorda that as her daughter she cannot leave the castle. Ico and Yorda attempt to reopen the path, but the Queen destroys part of the bridge; although Yorda tries to save him, Ico falls off the bridge and loses consciousness.
Ico awakens below the castle and travels back to the upper levels, finding a magic sword able to dispel the shadow creatures. After discovering that Yorda has been turned into stone by the Queen, he seeks out the Queen in her throne room. The Queen reveals that she is preventing Yorda from leaving so that she may extend her own life, which she had previously done by draining the life of those placed in the sarcophagi; now, she plans to restart her life anew by taking possession of Yorda's body. Ico and the Queen fight, Ico breaking both of his horns in the process. Ico is able to slay the Queen with the magic sword, but with her death the castle begins to collapse around him, and he loses consciousness again from falling debris. The Queen's spell on Yorda is broken, and a shadow version of Yorda carries Ico safely out of the castle and onto a boat, sending him to drift to the nearby shore and choosing not to accompany him. Ico awakens to find the distant castle in ruins, and Yorda, in her human form, washed up nearby him. She awakens just before the game ends.
- Ico originaly began as a PlayStation title which started devolpment in 1997. The bonus DVD that came with the Japanese version of Shadow of the Colossus shows the PS1 devolpment video. In the original version shown in the video, Ico was the main character, while in the FMV's, Yorda was the main character. It was believed that when Yorda was a main character, she was planned to be kept in a cage similar to in the real game, while Ico would have been a servant to the castle, finds Yorda, and they both escape. In 2000, the project was moved to the PS2 due to hardware limitations (as revealed by a Naughty Dog member in a interview with Pop Fiction, a GameTrailers series, that the PS1 only had 2MB of memory, because of this, either the team had to limit many of the content to fit the PS1 or move the project to the PS2), instead of the shadow beasts, it looked like guards were going to attack the player, and Ico (or Yorda) seems to have much larger and spiral shaped horns as opposed to his bull shaped horns. Yorda in the FMV seems to have a tatoo of what seems to be a sword on her arm.
- Even though Ico is a Japanese game, the game was first relased in North America, however because of this, many parts of the game were removed to meet Sony Computer Entertainment America's deadline. This included:
- 2 player mode, in which player 2 controlled Yorda, she may move freely and do many of the things she does in the 1 player mode, however she still cannot fight.
- The Watermelon Ending, in which in one part of the beach, there are many watermelons, if Ico picks it up and brings it to where Yorda is, the game ends with one final shot of Ico and Yorda eating watermelon on the beach.
- Yorda's Speech is translated in English & Japanese
- The Shining Sword, which is obtained after completing a puzzle. It has a very long reach while holding Yorda's hand, and is known to look and sound like a lightsaber from Star Wars
- Film-Grain Effects, which allows the game to look like a old fashioned film.
- The U.S boxart for the game was changed to make it seems more apporpite for an American audience.
- A book on Ico was released in 2004 and translated by Viz Media in 2011 known as Ico: Castle in the Mist.
- The game's credits theme, You Were There, was sung by a former member of the group Libera, named Steven Geraghty.
- Accourding to Team Ico and Fumito Ueda, Ico is intended to be a sequel to Shadow of the Colossus, as it ties in with it's ending cutscene.
- Fumito Ueda cites the games Another World, Lemmings, Flashback and Prince of Persia as the main influences for this game.