Okja is a most remarkable pig. As big as a medium-sized elephant, with a snout that looks more canine than porcine, she is slobbery and sometimes flatulent, but also loyal, gentle and brave. Okja is devoted, above all, to a girl named Mija. They have grown up together on a remote mountain farm that belongs to Mija’s grandfather, inseparable companions in a classic literary and cinematic tradition.

But anyone familiar with that tradition — I’ll mention “Old Yeller” and leave it at that — knows that stories of children and their pets are almost inevitably shadowed by tragedy and loss. The adult human world regards animals through a callous, utilitarian lens, as sources of food, labor or ornamental cuteness, a fact that “Okja,” Bong Joon-ho’s wonderful new film, takes to a dystopian but also an unnervingly realistic extreme.

The bond between Okja and Mija, who is an orphan, is the result of a contract neither one of them has read or signed. The pig is the physical and intellectual property of a multinational corporation, and as such she’s destined not only for the usual slaughter but also for crass and cynical commercial exploitation. The girl, a serious and stubborn child (played with heroic dignity by An Seo Hyun), is fated to lose her only friend.