Ajin is a thrilling supernatural horror anime to watch, the story was well-paced, action-packed, and very interesting. TLDR: this is a perfect anime to binge-watch.
Although it is a very good anime, I can’t quite place it as an excellent anime. My first gripe with the anime is largely due to the 3D CG that was used throughout the show. The characters appeared odd at first, however, I got used to it by the end of the first season. Frame by frame, everything looks ok, but the movement often felt offputting– which in a weird way added to the horror/dark component of the anime.
Second, the anime was thrilling to watch and it had enough plot depth to make it interesting, but it didn’t really have a deeper meaning. Another anime that I would closely relate Ajin to is Death Note. Death Note constantly tore into a philosophical debate surrounding justice and how power changes people. The closest thing that Ajin has to that is that it explores the ways in which people are marginalized if they are different– people with Ajin people being hunted down and researched on. Again, this topic can be really interesting if done right — like in season 4 of Attack on Titan when it introduced moral ambiguity and conflicting ideals between the main characters over the use of the Titan power. The discussion around human rights in Ajin is not deeply explored and becomes a simple black and white issue that only serves to advance the plot for the main villain. By the end of season two, the human rights issue for the Ajins has been resolved in the blink of an eye, leaving season three to be merely about fighting Satou. But, this might be too critical since it is a relatively shorter anime and didn’t have enough time to fully explore any themes/philosophical things deeper.
For a Shounen protagonist, Kei is different since he is… as his sister put it: “a Jerk”. There is some plot development with Kei since he eventually learns to trust and rely on others for support. However, Kei still remains a cold and detached protagonist for the most part. It is not clear whether this is due to his upbringing in a strict family, or if it has to do with his Ajin powers. Other than Kei, the other characters are pretty straightforward for anime. The supporting characters are supporting, and the antagonist is driven by the desire to conquer the world.