- Awesome Music:
- Complete Monster: The anime version of Ajin Sato(u), real name Samuel T. OBrian, is a former member of the US special forces discharged for insubordination, caused by his strong appetite for killing. Learning of his immortality in Japan, he plans to plunge Japan into terror while falsely claiming to work for Ajin liberation. Forming an Ajin terrorist ring through manipulation and treachery, his attacks include toppling a building into a heavily manned company headquarters, going in with said building and killing his way out of responding police units, and assassinating 15 government and corporation officials, all the while killing everyone in his way. In his final attack, he steals 20 units of nerve gas, takes over a JSDF base, arms the gas on missiles, and demands the Japanese government to submit Japan to his rule within one week or else he will exterminate Japan and rule over the remains. When the government compromises some islands for Ajin governance, Satou rejects the offer as "boring" and prematurely fires a missile at the Prime Minister's office, killing an untold number of people in a massive radius, shocking even his subordinates and causing many to defect. Along the way, Satou had formed a grudge with Ajin Nagai Kei, always preparing to decapitate Kei note and murder people Kei had cared about in front of his eyes. Badass and charismatic, Satou is ultimately violent to the core.
- Darkness-Induced Audience Apathy: On the basis of the large number of self-serving and amoral characters, it can become very hard to care about anyone, whether Ajin or government.
- Evil Is Cool: Yes, Sato might be a villain to the core, but he's just so awesome at it (see Magnificent Bastard below) that the fandoms in both Japan and the west love him. Judging by comment sections, he's the most popular character in the series by a safe margin, due to his clever tactics, charisma and general badassery.
- Limited Animation: While not to excess, when watched back to back Polygon Pictures's style is much more applicable to settings like Knights of Sidonia with vacuum and null gravity than portraying a mundane setting. In particular when characters are still they would have some motion by floating, instead of being Uncanny Valley inducing mannequins.
- Magnificent Bastard:
- Sato. He consistently makes impressive use of his abilities to take on impossible odds with complete nonchalance. Notably, his plan to infiltrate the security building Kei defends is brilliant in its simplicity: he cuts off and deep-fries his hand, sends it to the staff amidst a box of fried chicken, then destroys his entire body to regenerate from the largest piece, i.e. that hand. Which at that point was on the security staff's dinner table. Yeah. His plane hijacking strategy was damn good too. There's also one of his assassinations, where his whole plan is to drop an entire skyscraper on his target!
- Kei can hold his own pretty well, once he starts trying.
- Stupid Evil: The Japanese government. Ultimately, Satou is able to gather so many followers on account of the government's cruel, callous and inhumane actions toward the Japanese Ajin, leaving many to feel that they have no choice but to align with Satou in order to avoid an eternity of suffering and torture. Had Ajin been treated in a similarly humane fashion as they are in the US, Satou's task would have been much harder.
- Writer Revolt: The writer left early into the project and the artist took over, which is when the plot took a radical shift and Kei became a sociopath.
- The anime foreshadows Kei's sociopathy earlier by introducing Eriko, his little sister, earlier in the plot, and showing her rather antagonistic behavior towards her brother, making viewers wonder why she acts that way towards him.
YMMV / Ajin