The film will conclude the story of season 3 on the case of the "Foxes" being pursued by Unit 1, the Bifrost mystery, and Arata and Kei's battle. (Source: ANN)
First Inspector is a strong performance for the Psycho Pass series as a whole, not just Season 3. The animation quality might possibly be the series’ best yet. However, while the movie wrapped up most plotlines for the season and could easily work as the series’ ending, there were quite a few mysteries left unresolved and a few introduced. Though, the main goal here was to wrap up Bifrost cleanly, and it accomplished that well.
First Inspector breaks from normal Psycho-Pass tradition, though, with mixed results. As Director Shiotani noted, the movie gave less focus on the fight scenes. This worked well for Arata and Azusawa and flesh out the ideological rivalry between the two characters, making the final culmination of their fight very satisfying. While there were still an abundance of fight scenes, the pace of the story didn’t keep you fixated on the fights like before.
The movie was well written and high-octane, though Season 3 could’ve done a little better in the lead-up.
There are two plotlines the movie excels at, though. The first is the passing of the torch between old Division 1 and new Division 1, which is developed quite nicely, save for Kogami hating Kei for some mysterious reason. Second is the Sibyl System and the gore of the series. Sibyl has become more of a human entity over the course of Season 3, and the cast is not at death’s door, so you no longer have to feel guilty when things are going well.
Akane’s plotline is still left unresolved but appears to be merely a plot device for Season 3. Kei’s defection to the dark side in the Season 3 opening ended up merely being a red herring.
Homura ended up being a good guy as many anticipated, though there’s still a lot of mystery to him. Though as he appears to be joining the main cast, he’ll be the main source of excitement heading into season 4.
There were a lot of pleasant callbacks to Season 1. Though, Kogami seemed out of character in First Inspector, and perhaps it’s signaling he’ll be sidelined (living happily with Akane maybe?) for a new flagship character as Psycho-Pass moves forward.
Mostly importantly, though, Ubukata completely reestablished himself as a competent writer, so the series can move on with good standing regardless of whether Ubukata stays on or Urobuchi returns. Unfortunately, it doesn’t erase Psycho-Pass 2 from existence.