The important characters are...

The most important characters in the story will definitely be Friedrich and the narrator. The entire story revolves around Friedrich, everything is about him. The narrator also plays an important role, however, because he was Friedrich's close friend and looked at him from a different perspective. The narrator and his family tried to help Friedrich's family as much as they could. Ultimately, without Friedrich there would be no story, and without the narrator there would be no one to tell the story.

The other important characters will be the two families and Herr Resch. In the end, Herr Resch indirectly killed Friedrich by not letting him into the bombshelter, ending his miserable life