First season was at least following the manga. When I heard that the movie was announced I was excited but it didn't follow manga. They skipped part 2 of the manga and skipped part 3 as well. They took the aspect of the starting of part 2 in manga and the ending of part 3. At the end of season 1 it shows 6 months later a landslide occurs but in the movie 7 years later. The movie is completely non canon to the manga . If you want to consider it canon you can because it doesn't really affect the show story.
Tetsuo went to the landslide and met a detective. He found that the body was found of Matori and the detective asked him some questions. Then the plot goes on.
I liked the cast and story was good but compared to the manga it wasn't good. They skipped the village arc and didn't even explain properly that Tetsuo posted their story online.
Kubo said that Tetsuo made his killing more fun because he killed like 2 officers . Spoilers for the manga skip this part






SPOILERS
In the manga Kubo said thank you because Tetsuo let Kubo kills the entire village about 160 people and 180 because of suicide people.






Back to the movie
The music was on fire especially near the end of the movie. I like the cast so much especially Tetsuo.

One thing that the movie did better was show Tetsuo in Prison and gave a perfect Kyochi's character development. I really liked the scene where he punched Tetsuo( Hope he did the same in manga but he didn't because of his friends) I also loved that Kyochi was more involved in the action.
Choreography was amazing in the movie. I hope that they make season 2 of the series other wise this movie will be show canon which isn't bad but manga is amazing;