They're not. The anime took a separate path near the end due to a lack of its popularity and decided to quickly conclude the story. However, it's not that much independent from the manga and did retain a lot of elements from the original story. That manga's nearing its conclusion and by the looks of it, it'll have a similar ending. As for the characters, almost none of them are alive and even more have foreshadowed deaths in the manga. By the time the story in the manga ends, almost all of them will likely be dead, similarly to the anime.