The narrator of a novel could be the protagonist of the story, a third party, or a voice-over. In most cases, the narrators were the protagonists of the story because this allowed the readers to be more involved in the plot and better understand the characters and events in the story. However, sometimes there might be a third party or a voice-over to narrate the story. This would make the story more objective and comprehensive, allowing the readers to better understand the background and truth of the entire incident.
Armin could be the storyteller. Sometimes characters take on this role to provide a unique viewpoint or to drive the narrative in a particular direction. But we need to know more about the story to confirm it for sure.
Armin is still alive in the manga. The story developments don't result in his demise. His presence remains significant and continues to shape the narrative.
A distinct voice is crucial. For example, if a narrator has a very deep or very high - pitched voice that stands out, like Morgan Freeman's voice which is deep and commanding, it can make the story more memorable. And if they can use their voice to create different emotions, like excitement or sadness, it helps children get more into the story.