It's an Oscar-nominated animated film by Mamoru Hosoda (The Girl Who Leapt Through Time, Summer Wars, Wolf Children, The Boy and the Beast), about a four-year old boy (Kun), his newborn sister (Mirai) and their family. When Tomoko and I watched it, we were probably the toughest audience you could get. Our daughter Misaki was three years old and just like Kun (maddening, irrational, barely sentient) and we also had an eight-year-old son for comparison. As an animated portrayal of tiny children, it's superb. Tomoko described watching the film as like watching herself.
Tomoko hated the film. I found it interesting.
Kun is a brat. Normal for his age and with razor-accurate characterisation, but a brat. He'll insist on impossible things and he lives in a world of anti-logic. If he wants something, minor details like the laws of physics won't persuade him to shut him up. Mind you, his jealousy towards his baby sister in the early scenes is his parents' fault, since they neglected him in the rush of "yikes new baby" and his reaction is natural and well known.
If you hate children, you'll want to throw Kun through a window. If you're a mother with a child Kun's age, you'll recognise his behaviour to a degree that's almost painful and you too might want to throw him through a window.
It is, though, a superb portrayal... visually. Unfortunately, they cast an 18-year-old girl with no voice acting experience. She's awful. Absolutely dire. She doesn't sound like a four-year-old, which cripples the film. (The main characters are all played by screen actors, not voice actors, but that's only a problem with Kun.) There's a not dissimilar moment elsewhere, though, when we're time-travelling back to when Kun's mother was his age. Her mother, i.e. his grandmother, is played by Yoshiko Miyazaki and she sounds fine in the rest of the film, when the character's granny-aged, but she sounds crashingly wrong as the mother of a four-year-old.
Oh, and occasionally the film gives its four-year-olds unrealistically sophisticated vocabulary. Would Kun's mother really have known one particular word, for instance? (That's in Japanese only. I've no idea whether or not these problems were fixed in the English dub.)
The film then gets magical. Kun talks to a member of his family who got jealous for a while on the arrival of a baby. The offender was Kun himself and the jealous person was their pet dog (here transformed into a human). Mirai travels back from the future as a teenager, but she's still calling Kun "big brother". Kun sees his mother, father and great-grandfather in their youth. Eventually, he runs away from home, gets on an impossible train, talks to an impossible station attendant (animated in a completely different style) and is told that he might have to get put on a special bullet train in a pit.
This isn't a plot-driven film. It's more a bunch of interlocking, whimsical character studies that add up to family insights. Kun concludes early on that he's a bad brother and worthless, but it's demonstrated that everyone is, to put it mildly, flawed. Mum was far worse than him when she was his age, then on having a second baby made that very basic parenting mistake I've already mentioned. Dad means well, but he's appalling in that scene where he's not listening as Kun tries to talk to him. (In another scene, he admits to having been a workaholic who wasn't there for Kun as a baby.) Even granny looks to me like a failure as a mother to have raised a four-year-old like that. (The only thing we experience her doing in the past is yelling.)
They improve, though. They chill out. Dad becomes a competent house-husband. Mum and granny get on fine now they've grown up and can have relaxed chats in the kitchen. Kun does indeed become a good big brother.
This film is a superb portrayal of children and parenthood... but it's also flawed. Look, for instance, at the scene where children are sneaking up to try to pluck something off Dad's trousers. It's gorgeously animated. It's wonderful to see. However, it doesn't make sense, since Dad would hardly have noticed had four-year-old Kun just walked up and plucked that stick off his bottom.
Tomoko found the film preachy. I see what she means, but I think it's enigmatic enough for the audience to find their own message. It's portraying the web of what we are, the interlocking relationships and luck over the generations and the ways in which we grow. It also has a protagonist without the mental capacity to process anything beyond "GRANDAD COOL ON BIKE!!!", making the film's lessons invisible to everyone in it. It's interesting. If you watch this with someone, you'll have a lot to discuss afterwards. I'm tempted to show it to Misaki in a year or two and see what she thinks.