If you've seen an anime movie based on a long-running shonen manga, then you've seen The Seven Deadly Sins: Prisoners of the Sky. The usual symptoms of a shonen filler film are on display here: an undercooked plot that is irrelevant to the overarching story of the manga, battles with no narrative tension that only serve to give each character from the sprawling cast their one minute of spotlight, and side characters and villains who are basically just reskins of pre-existing characters from the series. (Prisoners of the Sky is particularly dreadful about this one; Sorada and Elatte are Meliodas and Elizabeth clones but with wings.)

Right from the outset, Prisoners of the Sky was never going to be a substantial experience, but it does scratch an itch the way all the good Shonen Films do: the story is a self-contained mini-arc that puts the characters in an interesting scenario that you normally wouldn't see them in. In this case, there's fun to be had in the mistaken identity antics, which take up a good portion of the early part of the film. Fans of the pig mascot character Hawk and his mother, the giant green pig that carries the Boar Hat bar, will probably be pleased by their escapades in this film.

The film opens with its best gags. Meliodas stumbles onto the Sky Palace, a land in the sky where everyone has wings, and is promptly mistaken for Sorada, the son of a warrior who has escaped to the earth. Sorada, for his part, comes across the Seven Deadly Sins and is mistaken as one of their own. I cracked up at a scene where Diane accidentally steps on Ban and reduces him to a bloodstain as Sorada watches in horror. Not only is it a moment of cartoony violence straight out of the Looney Tunes, it gets all the obligatory character introductions across without bogging the pace.

Unfortunately, the story doesn't stay light and breezy for long, as it's soon revealed that the Sky Palace is under attack by demons. It's not a terribly interesting plot, especially since most of the developments can be seen from a mile way, but the comic relief still shines. Meliodas is his usual blasé self even as a fish out of water. He also goes around shirtless for most of the movie, probably because his muscles make it easier to differentiate between him and Sorada. Meanwhile, Hawk gets mistaken for a pig-like deity figure called “Oshiro-sama”, which inflates his ego even more than usual. He also gets his own chance to fight in battle, and the result is just as amusing as you'd expect.

There are some other bright spots in an otherwise milquetoast plot. Meliodas's own status as a demon gives him a connection to the Sky People that fits in rather seamlessly with the overall lore of the series. There are a couple of moments when the lore is applied quite cleverly, and which definitely took me off guard. Otherwise, there really aren't any twists to this story. There's never any doubt that The Seven Deadly Sins will help out the Sky People, nor are there any conflicts between the two groups beyond some initial confusion, which the characters quickly take in stride. When the fighting breaks out, every Seven Deadly Sin is already conveniently in place to engage in battle.

And that brings me to the real focal point of the film: the action animation. What the battles may lack in narrative tension they compensate with technical brilliance. I've always liked the action animation in the TV series, which constantly delivered standout moments without ever sacrificing the overall consistency. The movie's animation is roughly on par with the TV series until it reaches the extended action sequences near the end. Then things get wild (in a good way!). It's satisfying to watch moves that you're familiar with from the series drawn out with even more effects and detail. The storyboards and layouts get more creative as well, which makes each and every one of those battles against the film's throwaway villains stand out. The film was directed by Yasuto Nishikata, a relatively new face who has honed his skills as a Bleach episode director, but it was supervised by Noriyuki Abe, the master shonen action director. That probably helps explain why those action scenes flow so well.

In all other areas, the film retains the core strengths of the TV series. Hiroyuki Sawano and Takafumi Wada's soundtrack is great, especially at capturing the intensity of the battle scenes. Even though we've heard it in the TV series several times now, it never stops being awesome when the “Perfect Time” insert song starts playing during a battle. I'm not as big a fan of the ED song performed by Nogizaka46, which didn't feel as if it fit the tone of the anime, but at least it doesn't play during the film itself.

All in all, The Seven Deadly Sins: Prisoners of the Sky is a serviceably popcorn film that delivers about as much as you'd reasonably expect from a shonen filler movie. Although some parts of the setting tie into the main series quite cleverly, it's not consequential to the overarching story at all and will probably be quickly forgotten. At least I'm happy with the action scenes and gags that came out of it, as they're some of the best the series has to offer. It's not essential, but it is fun, and that's all you need for a good time.

One other thing I should mention for fans interested in watching the film is that it's set after season 2, which means that all seven of the Seven Deadly Sins appear in it. The film doesn't spoil any specific events for season 2, however, and most of the Sins are only really in it for their one cool battle scene, so it's probably fine to watch this film even after season 1. In fact, it may even be better to watch the film before season 2 because a certain scene will have more impact that way. But it really doesn't matter either way.