I had fun watching this.

Story
After all the torture they put him through I thought he would gladly take revenge but he didn't. He is one of those characters who have morals and conscience.
The story is not developed enough and the characters don't have personalities.
It's fun to watch as something where you turn off your brain.

Things I liked
- The music.
- Creativity in fight scenes. They can't die so it's interesting to watch them fight. There are no limits, they shot themselves and start again.
- The concept of Ajin.
- Cinematography, it's pretty.
- The ending. It's awesome.

That's it. It's a pretty movie without much story and depth.

Things that could have been better
- The characters are one dimensional. They have no personality or character development.
- Nagai starts as a confused and weak guy but by the end of the movie he can fight and he is a great strategist. When did that happen?
We see him train but it's short and not enough to convince us that he can take on Satou who has way more experience than him.
- The sister subplot just takes time and makes no sense. She didn't serve any purpose in the story.
- Why is the bodyguard on human side protecting the bad guy?
- That one scene where the guy dies and Nagai is super sad. Why? Just why? I don't care about that guy, why are you trying to make it emotional? Why should Nagai care about him when he was one of the guys who tortured him. Just kill him and move on, don't try to make it emotional.
- Satou's plan. Why couldn't he just take revenge on people who hurt him? At the end he didn't do anything and that made me sad. I wanted the glasses guy to suffer.

Overall, a cool movie. I think it's worth watching.
It would be nice if there is a sequel because there is so much potential in the story.