4 stars

Happiness doesn't get enough press of late, because of course, everything is depressing. And so this Japanese anime film is a breath of fresh air.

It's a musical, not everyone's cup of tea, but the handful of musical numbers have definite context, and as this is anime, breaking into song is more believable than in, say, Grease.

In a picturesque town in the north of Japan, students at the local high school welcome new transfer student Shion (voice work by Tao Tsuchiya in the Japanese language version playing in Canberra).

Most of the town works for the major artificial intelligence company whose twin office skyscrapers dominate the local skyline, and so a new face in school is a welcome addition.

Shion is cute and engaging and so her fellow students don't seem to mind some of her quirky behaviour, like breaking into song. Shion seems to already know the class outcast Satomi (Haruka Fukuhara), striding up to her and asking if Satomi is happy.

Satomi, however, knows Shion's secret. Shion is an AI, a robot, even if one so convincingly made that she can pass as human. Satomi's mother is an AI coder and program leader at the robotics company and Satomi has accidentally read her mother's calendar that noted her new robot was headed to the local high school for a week of secret testing.

When something goes wrong on the first day and Shion shorts out, revealing herself to be a robot, Satomi begs the handful of students who witness the technical meltdown to help keep Shion's secret.

These students are the friends that deserted Satomi some years earlier - school dreamboat Gocchan (Kazuyuki Okitsu); and his girlfriend Aya (Mikako Komatsu), the Judo-obsessive Thunder (Satoshi Hino) and tech wiz Toma (Asuka Kudoh).

Explaining that her mother's career depends on this trial being successful - Shion making it through a week of school passing as human - Toma helps wipe the corrupted files in Shion's system and the kids fill their week helping their new robot friend pass a human.

It doesn't help that Shion's behaviour gets increasingly erratic, with a few more public bouts of singing. But the overwhelming positivity of the AI girl has an impact on the students. She helps Thunder overcome his performance nerves before his first big Judo competition. Winning the tournament makes Thunder Shion's greatest defender.

The fractured relationship between Gocchan and Aya is healed by Shion, and she then turns her attention to the long-soured friendship between Satomi and Toma.

But despite all the best efforts of the students to help their AI friend, the AI company's local boss is determined to ruin the experiment.

Sing a Bit of Harmony comes from Japanese studio JC Staff and funded by the Japanese mega-studio Shochiku. The animation work is top-notch, a step up from most anime.

But the film's secret weapon is the screenplay by Yasuhiro Yoshiura and Ichiro Okouchi. Genuinely moving, the script effectively builds pace and tension and gives the characters enough backstory and motivation that they don't come across as, forgive me, two-dimensional.

We got a new puppy at our house just before Christmas and we have, in a way, been programming this new creature. She has been learning to sit and stay, but also learning that she is loved, and to love in return.

This real-life coding project I'm in the middle of might be why I really enjoyed this storyline and the infectious puppy-like optimism of Shion. I was genuinely moved by the film's final scenes.

The film's musical numbers by Yohei Matsui and Ryo Takahashi are as fun as anything in Encanto.