Plenty of video games are about power, violence, action, struggle and competition. Rather fewer are about friendship, gratitude, care, respect and compassion. “The Last Guardian”, a breathtakingly thoughtful Japanese game about a boy and a gigantic creature escaping a ruined megastructure, offers a potent reminder of the possibilities of the medium.

It’s something of a miracle that “The Last Guardian” is here at all. Announced in 2007 for the then-new Playstation 3 console, it was billed as the third part in a loosely connected sequence of games by Fumito Ueda, a Japanese artist and designer. His previous games, “Ico” (2001) and “Shadow of the Colossus” (2005), were already famous, as much for their fascination with emotional states as for the lunar strangeness of their design. In one, a tiny horned boy made his way around a vast, deserted fortress, leading a ghostly girl by the hand and dodging malevolent creatures. In the other, a lone horseman rode through an endless, abandoned country, mournfully dispatching huge beasts to bring back the spirit of his departed lover. There was almost no dialogue. These were esoteric puzzle games, played out in an atmosphere as eerie and affecting as a De Chirico painting.

But “The Last Guardian” failed to arrive on schedule. Development hell is common in Hollywood, where ideas and scripts can kick about for years before entering production, but rarer in video games, where projects tend to be planned for specific hardware which will soon be updated or replaced. In 2011, when “The Last Guardian” was already overdue, Sony announced that Ueda had left their employment but would continue to consult as a freelancer; two years later, with the new Playstation 4 on the horizon, his game was presumed missing in action. Now it is here, back from the dead.

“The Last Guardian” revolves around the relationship between a small tattooed boy and a gigantic beast called Trico, a fantastical hybrid of bird, cat and dog with wings, feathers and horns. At the beginning, both characters are discovered unconscious on the stone floor of a dungeon. You control the boy, and your first task is to remove Trico’s huge leather muzzle, break the chain around its neck and pull several broken spears from its bloody flanks. Naturally, the beast is mistrustful: it roars, twitches and lashes out with sufficient force to knock the boy unconscious. You then have to win its trust, calm it down, find it something to eat – and form a bond with it.

The game’s creators have considered this relationship with extraordinary sensitivity and detail. Plenty of video games provide the player with a companion, but inevitably one of the second rank, there to be bossed about or protected. Lydia, the sword-swinging shieldmaiden in “Skyrim”, charges into battle on your behalf; the door-kicking squadmates in “Call of Duty” unload their weapons into your enemies. “The Last Guardian”, by contrast, gives you a vast and dangerous companion, lifelike, basically unknowable in its motives, and with what seems like a mind of its own. Trico ruffles its feathers, sniffs the air, scratches behind its ear with a huge scaled claw, and (initially, at least) demonstrates only a mild, cat-like interest in your actions. It follows you around because you’re there; if you want it to do anything else, you have to ask it.

Ask, not tell. Communicating with Trico is the game’s most fascinating task, and the bond with this imaginary character is stronger than anything I’ve experienced in games. Using combinations of buttons, you can call Trico and point out places for it to go to, mount its sides like a climbing wall and request that it jump, or stomp or climb. Sometimes it will obey you, and sometimes it won’t. Since the character is a small boy, it’s Trico who deals with combat in the game, whacking to bits the animated suits of armour that stalk the corridors of the enormous castle. After a fight, it leaps about like a skittish horse and has to be soothed and stroked back to repose. I suspect that Trico is programmed to interact with you in proportion to how often you talk to it, stroke it, feed it, pull out the sharp ends of embedded weapons and mop the blood from its straggly feathers.

Ueda has put a lot of work into making the environment intelligible through this relationship as well. Most game-worlds can be read as codes of possibility: can I jump there? Can I kill that? Navigating the castle in “The Last Guardian”, full of mysterious symbols, arcane mechanisms and tantalisingly obscure architecture, you soon begin to interpret it in a different way. Can I persuade the creature to do this? Will it be frightened to do that? It’s a subtle emotional transfer but a significant one, and it underpins the narrative of “The Last Guardian”, which is built not from grand moments of disquisitional dialogue but on sudden demonstrations of affection, bravery, gratitude and self-sacrifice.

Set against this, the game’s minor faults – occasionally dodgy camera control, the hardware sometimes labouring to render the stunning and vertiginous landscapes – pale into insignificance. “The Last Guardian” is the most emotionally involving game I’ve ever played, a work of art that uses the interactive possibilities of its medium in a wholly unexpected way. There’s nothing else like it. Thank heavens it got here in the end.