How does the adaptation differ from the original source?
Erased spoilers ahead!
Erased (Boku dake ga Inai Machi) is a mystery drama series, that follows 29-year-old Satoru Fujinuma. He is revealed to have the ability to travel a few minutes back in time to the moment before an accident in order to prevent it. But this time his ability worked a bit differently: he finds himself in his school self, and now he has to unveil a kidnapping mystery and prevent horrible things from happening.
The anime adaptation is overall very close to the manga, but fans mention some alterations in the ending. The main conflict ends up pretty much the same: with the confrontation of Satoru and his ex teacher who turned out to be the murderer, Gaku Yashiro. After a years long coma, Satoru finally wakes up, and the teacher is eager to find out how the boy learned the truth, talk to him and kill him. In the manga, their final encounter happens on a bridge. Yashiro intends to burn the bridge down, killing both Satoru and himself. The anime shows their confrontation on the roof of the hospital, where the ex-teacher threatens to kill the boy. Satoru survives and Yashiro gets arrested in both of the endings.
Fans say that the anime ending is, although rushed, cannot be called a bad one.
They also add that the manga ending is much longer and it gives more closure and explanation as well as more depth into some characters. While the anime fixes some manga problems, there's a belief that 3-4 more episodes would make the story better and leave the audience more satisfied with the conclusion.
The pacing is another thing that is different from the original source. The manga has 44 chapters, and it was impossible to delve into all its aspects in 12 episodes. This led to the anime moving at a faster pace and being more intense, which is not necessarily a bad thing.
Anyway, no matter the differences, the outcome of the series is the same in both types of media. Some alterations in the adaptation ending might be explained due to the anime being in production while the manga wasn't finished yet. However, fans don't suggest dropping the anime and reading the manga instead. They think it would be a good idea to finish the adaptation and then get acquainted with the source material and see the difference for yourself.