A frazzled widowed mother, Saori (Sakura Andô), suspects that all is not well with her preteen son, Minato (Soya Kurokawa). The boy seems subdued and withdrawn; she catches him hacking inches from his mop of hair. He asks odd, troubling questions: if the brain of a pig was transplanted into a human, what would the resulting creature be, human or pig? Or some kind of monster? And then there are the injuries – an ear yanked so brutally that it bleeds; a livid facial bruise. Saori soon deduces that her son’s new teacher, Michitoshi Hori (Eita Nagayama), at his provincial Japanese elementary school, is responsible for her son’s brooding disquiet. She confronts the school principal (a confounding reflecting prism of a performance from veteran actor Yūko Tanaka), but is frustrated by the school’s response: a suffocating blanket of meaningless apologies designed to stifle her complaints. Saori is understandably angry: her son, after all, is the victim of a cruel teacher.

Or is he? The latest film from Hirokazu Kore-eda (Shoplifters), and the first since 1995’s Maborosi that he didn’t also write or co-write (the screenplay is by Yūji Sakamoto), rewinds to the beginning of the story – a burning building is a marker point – and replays key scenes, fleshing out the tale, this time from the perspective of the well-meaning teacher. Hori feels, perhaps fairly, that he is being thrown to the wolves by the school authorities (“What actually happened does not matter,” says the chillingly dispassionate headteacher). His view of the classroom dynamic is that Minato is a bully who has systematically targeted a smaller, weirder child, Yori (Hinata Hiiragi), the social outcast of his class.

But then we rewind again, and the story plays out from the point of view of the two boys, showing the fragile new growth of a tentative friendship and the beginning of an understanding of deeper feelings for each other. The kind of feelings that Yori’s drunken, boorish father already suspects in his sensitive son, and is prepared to beat out of him.

It’s a difficult thing to pull off without it feeling a little disingenuous. This structure – the Rashomon technique of offering different perspectives on a single story, with each new angle subtly shifting the audience’s view – is by its nature manipulative. It only works when we, the viewers, accept that the film-maker is deliberately misleading us through selective omission and unreliable witness accounts; when we agree to be led astray and then guided toward some kind of truth and resolution.

Monster is an interesting case. Aided by a delicate, crystalline score by the late Ryuichi Sakamoto, Kore-eda deftly carries us through the shifting perspectives of the story with an ease born of extensive practice – the director of films such as Broker and Our Little Sister is no stranger to elegantly handled emotional manipulation, after all. There are a few too many red herrings, and some nagging questions. Why, for example, if the teacher suspected that Yori was being bullied by Minato, did he somehow fail to notice the campaign of terror being run by the other little shits in the class?

But when it comes to the payoff, that satisfying clincher that ties everything together, we are confronted with not one but two starkly contrasting readings of the ultimate “truth” at the end, one optimistic of a new start, the other involving the deaths of several characters. After the first viewing I veered emphatically towards the bleaker option. A rewatch opened up the possibility that the more hopeful take was the correct one. For what it’s worth, Kore-eda said after the film’s Cannes premiere that the cast and crew opted for the positive reading of events, but he conceded that the tragic interpretation was equally valid.

Does it matter that there is such ambiguity about the film’s ending? Perhaps not as much as you might expect, although there’s a sense that Monster pulls its punches throughout, forever stopping short of making a bold statement. The decision to focus on the relationship between pre-adolescents rather than older children is a key example – the film hints at questions of sexuality but neatly sidesteps actual sex. Ultimately, the question of what actually happened is just another red herring. The real point of the film is its heartfelt, if slightly trite, message: that it’s the wider world that needs to adapt and accept the differences of children like Minato and Yori, rather than the other way around.