Ajin is a prime example of what happens when movie producers, writers, and filmmakers don't respect the original material and just create a live action adaptation of a popular manga/anime series for the cash grab. I can think of only one word for the movie, “kudaranai”, which means pointless. Although it has a great cast of actors, none of them (except one) are appropriate for the parts. With the exception of Tamayama Tetsuji as Tosaki, the rest of the cast don't look or act like the characters in the original series. Nagai Kei is supposedly a 17-year-old high school student aspiring to become a doctor and yet they chose to cast a nearly 30-year-old Sato Takeru. Instead of casting a suitable actor for the part, they changed the character into a 26-year-old med student to fit the actor they've chosen. I would have been fine with this change if they had bothered to actually give depth to the character and explained his motivations instead of just making him an unusually intelligent young man whose intentions are not quite clear.

Nagai is not your garden variety ajin, his IBM and black ghost first appeared when he was just a baby so he has an excessive amount of the stuff, allowing him to call upon his black ghost multiple times unlike most ajin. He also has low emotional intelligence, making him almost emotionless, cold, and indifferent. But he's incredibly smart and observant, allowing him to think more logically and strategically. None of those things are explored in the movie. Shirota Yuu as Tanaka is just a waste. With the way they wrote the character, he could have been played by basically anyone, there was no need for them to hire a popular actor. Shimomura is reduced to a mere sidekick, not one bit of character background is given. But my biggest disappointment is Sato. Ayano Go may be one of the most popular actors in Japan these days but his acting talents simply cannot make anyone believe he's actually an elderly man. Sato is not even Japanese! His real name is Samuel T. O'Brien (Owen in the manga), Sato is just the name he used when he came to Japan. He was born in the 50's and he's a war veteran with exceptional combat skills. He also appears to be a friendly and kind old man, that's why Nagai initially trusted him. He may be brutal and calculating but on the surface, he seems calm and respectable. By changing the age of the character, they completely scrapped this aspect of his persona. Ayano's portrayal comes off as psychopathic and warlike, the complexities of the character lost in his John Wick-like gun-fu. It's probably one of the worst casting choices I've ever seen.

Tamayama Tetsuji's portrayal of Tosaki is the only thing that remotely reminds me of the source material. But even his character has no real depth, his motivations are also unclear. The rest of the characters are as pointless as this movie, just mere fodder. The special effects are decent but could have been better. Why Japanese film producers continue to hire the same old popular actors instead of holding auditions and finding the perfect actors for the roles, escapes me. I am now utterly convinced that the anime stage play productions are so much better at adapting anime/manga series for they really try to remain faithful to the source material and cast the most appropriate actors they can find.