I didn't think it was just a narrator. I thought it was someone who knew them and tells the story to somebody else. However, I imagined the narrator was an old man. I didn't think even for a second that it might be a woman who tells us this story ( ̄∇ ̄") .
Am I the only one who read the narration with a man voice in my mind? That's crazy. I always thought it was just a narrator like in Dragon Ball.