Visually, Ajin is not particularly appealing especially if you watch in resolutions any lower than 720p. But the story is captivating as it explores the ethical aspects of humanity laden with conspiracies and cover-ups. It is also action packed with battles against terrorism that keeps viewers in suspense. The battles are satisfying to watch as there is no clear cut on who will win and lose once it starts - ajins with their immortality vs humans with their resources. Both sides try to outsmart each other just like how people in real life fight a war.
Ajin is often compared inferiorly to Tokyo Ghoul but Ajin is the better series in my opinion in terms of suspense, plot, and theme. It is also more realistic in the sense that that's how it would probably turn out in the real world if ajins exist given the ugliness of human nature, with how governments of the world would inhumanely exploit ajins for their own benefits, which eventually leads to somebody rising up in vengeance; in this case, terrorism. I also prefer this series because it cuts off emo bullshits (something you see a lot in Tokyo Ghoul) and focuses on the issue of stopping Sato.
I like the character designs overall. All without the emo looks and you can tell the difference of characters from the faces rather than the hairs and costumes. The MC is not a typical protagonist who preaches about friendship and sunshine and rainbows, but instead a calculative selfish asshole. He doesn't look particularly handsome either, which I find really refreshing.
Overall 9/10 from me. Recommended for mature viewers.
