Ga-eun Yoon’s The World of Us begins with an exclusionary ritual familiar to anybody who’s attended primary school: choosing teams. We watch a tight close-up of ten-year-old Sun’s (Soo-In Choi) face as, one by one, her classmates are picked before her. She’s the last choice for dodgeball – another fundamentally cruel childhood pastime – and from the look of resignation on her face, it’s a position she’s accustomed to.

The World of Us is a film of childhood friendship, and therefore it’s a film about such rituals of social segregation. The path from infancy to adulthood is a path from birthday parties where everyone’s invited to narrowly-defined cliques, and by focusing on prepubescence, the apex of that painful progression – when every friendship feels like the world, the first and the last and the everything – Ga-eun vividly reminds you of the depth of loneliness found in childhood.

Through bracelets and dyed nails, birthday parties and dodgeball, shared lunches and shared secrets, we follow the formation – and then the unravelling – of the tight-knit friendship between Sun and new student Jia (Hye-in Seol), who moves to Sun’s town at the beginning of the holidays. Outside of the confines of school social structures, the pair become fast friends, with their differences – how Jia’s house is so much nicer than Sun’s family’s cramped apartment, how Jia’s parents are absent from her life – rendered irrelevant by the closeness of their bond. It’s heartwarming, and simple, and true.

And ephemeral, of course. Jia attends a cram school – that Sun can’t afford – and there befriends the school bully, who sneers at Sun’s clothes. We know how the story goes from here, but it’s still heartbreaking to watch Jia ensconce herself within the ‘cool group’ at the expense of Sun, joining in her new friends’ teasing and betraying the trust they shared. It’s devastating because of the unostentatious proximity with which Ga-eun films these slender melodramatics, but also because it’s impossible not to relate to the aching sense of loss Sun feels.

The World of Us, in many ways, feels like a prepubescent, Korean version of Mélanie Laurent’s Breathe. Like that film, it closely interrogates the politics of female friendship; like that film, it feels like it could only have been made by a female filmmaker. It’s a simpler story, naturally; the younger characters don’t allow for the psychosexual tension humming under Breathe’s surface. It’s not as formally flashy as the French film, either, but its cinematographic subtlety is shared with an ending that sidesteps Laurent’s misguided gearshift into full-on thriller territory. This is a quieter film, and as – perhaps more – devastating for it.

Special mention must be made of the young cast. As befitting this kind of story, adults are shunted to the margins, possessing good intentions but little understanding, so the film’s emotional burden falls on the shoulders of young Soo-in and Hye-in. They’re each outstanding. Soo-in carries herself like a delicate vase, fragile and introverted. She keeps her eyes low, she huddles her body as though hiding away from the world; we see how much Sun’s friendship with Jia means through the littlest gestures – the widening of her eyes, the freeness of her movements. Jia has a fragility too, but also a boldness, a confidence that’s eroded over the course of the film as she faces her own social challenges. Stories like this don’t work without believable actors, and it’s a testament to these young actresses that The World of Us works so well.