After such expansive fantasies as Wolf Children  and Summer Wars , Japanese animation master Mamoru Hosoda delivers a story of such intimate, unpretentious simplicity, you’d hardly recognize it as coming from the ambitious visionary behind those films. And yet Mirai – which inventively depicts the way a young boy’s world is turned upside down by the arrival of a baby sister – could not have been made by anyone else. It’s the work of a true auteur (in what feels like his most personal film yet) […].
Who but Hosoda could have imagined a scenario – every bit as enchanted as Charles Dickens’ A Christmas Carol, though entirely original in its own right – in which four-year-old Kun comes to accept his initially unwelcome sister via a series of hallucinatory visitations from other members of his family: past (his war-hero grandfather and decades-younger mother), present (an anthropomorphic version of the pet dog), and future (Mirai, appearing as her later teenage self)?
But it’s the small real-world touches that make Mirai so charming […]. [E]motionally speaking, Mirai reaches deeper [than Hosoda’s previous films], aided by a lovely, featherweight score from Masakatsu Takagi, subtly reinforcing the gradual evolution of the boy’s attitude toward his kid sister.
Peter Debruge, Variety