The maker of Shoplifters and I Wish talks about Monster, his dark new film about our dangerously fragmented world – and the movie he’s planning about his dad, who endured horrors as a PoW in Russia

Film sets are like families, says Hirokazu Kore-eda. They are loose social structures, nominally hierarchical and ideally geared towards a common goal. While the Japanese director accepts that this puts him in the role of the father, he disputes the suggestion that this automatically makes him the boss. He supposes the cast are the children – often literally so. “The time we all spend together,” he says, “is very intense. The cast and crew become very important to me.” But at the end of each shoot, the unit collapses, the family members disperse and all that’s left are memories, mementoes and of course the actual movie itself.

This idea of the makeshift, sometimes impermanent household is a fascination for Kore-eda, who increasingly lives his life on the road, moving between film shoots and festivals. In the course of a 30-year career, he has cast his Japanese families in a variety of roles: as a band of thieves (the Palme d’Or-winning Shoplifters) and as a happy accident (Like Father, Like Son); an invisible society (Nobody Knows) and a triumph of magical thinking (I Wish). At best, he feels, the family unit provides a nurturing seedbed, or crucial social glue. At worst it’s a bubble, a prison, a trap. “It depends on the family,” he says. “But it also depends on the state of the world.”