User blog comment:Fire Eater/Differences between the manga and the anime?/@comment-1037137-20180718063138/@comment-24407809-20180718063851

Well, there's a possibility that everyone is jumping the gun in assuming that Keiji is being kept alive, and he may just be killed at the beginning of the next episode (I feel like that's the most likely outcome). But if he is kept alive, it will probably be so that the story can have a character on the Survey Corps' side to kill off in the battle at Reiss chapel, so that the fight isn't a completely one-sided victory for the Corps.

Also, Keiji was saved because he is the best character.