The House of Us (2019)

It's the summer holidays in the city and young Hana is trying to get her warring parents to reunite. But she's distracted from her quest one day by a couple of younger girls, 9-year-old Yoomi and 7-year-old Yoojin. As she swiftly becomes an older-sister figure to the pair, the trio's recess becomes one of imagination and adventure--from playing tricks on the landlady to going on a seaside reconnaissance--that leads to the bittersweet glimmerings of maturity.