There might be a human character who somehow gets involved with the angel of death. This human character could be on a quest or facing a personal crisis that intersects with the angel of death's existence. Maybe there is also a sidekick or a mentor - like figure that helps the main character navigate the strange world of the story.
I don't know as I haven't read it. But it might have the angel of death as a main character. There could also be characters who interact with the angel, like the ones whose lives are affected by it, such as the people it is sent to or those who try to stop it.
Without knowing the particular 'angel of death novel', we can only speculate about the main characters. The 'angel of death' would surely be a central figure. There could be a human character who is on a journey to understand the nature of death and in the process crosses paths with the 'angel of death'. Another possible main character could be a religious figure who believes in the concept of the 'angel of death' and tries to either communicate with it or prevent it from carrying out its deeds. And there might be a character who has been marked for death by the 'angel of death' and is fighting for their survival.
Sometimes, the main character could be a scholar or researcher who is studying angels in the context of the light novel's world. He discovers something extraordinary about angels that sets the whole plot in motion, and he has to deal with the consequences, whether it's political intrigue, facing otherworldly threats, or trying to convince others of his findings.
Since we don't have much information about this light novel, we can only make assumptions. There could be a lead character who is an average office employee. This person might be the one who first notices the strange 'angel - related' things in the office. There may also be a senior figure in the office, like a director, who has to deal with the consequences of this 'angel project' on the office operations. And of course, there could be the 'angel' characters themselves, who might have their own personalities and motives.
The main characters include Daisuke Niwa, who transforms into Dark Mousy. There's also Risa Harada, who Daisuke has feelings for. And Satoshi Hiwatari is another important character.
Obviously, Harry is one of the main characters since he's in the title. But without reading it, it's hard to say who else might be in it. There could be characters from the original source material that the fanfic is based on, like his friends or enemies. Maybe there are also new characters created specifically for this fanfic that interact with Harry in his role as the angel of death.
I'm not entirely sure as I haven't read or watched it in full. But likely there is the 'angel next door' character, who is probably the central focus. There might also be neighbors or friends who interact with this character and help to develop the story.
The main character is definitely Alita. She's a cyborg who wakes up with no memories. There are also likely other characters such as Hugo, who might be a friend or love interest of Alita. And then there are the villains in the story who oppose Alita and try to stop her from achieving her goals, though their specific identities would be more detailed in the actual light novel.
I'm not sure as I haven't read it. But it could be the 'angel next door' character herself and perhaps a neighbor or someone she has a special connection with in the story.
Since it's called 'the angel next door light novel', there's probably a character who is seen as the 'angel next door'. There may also be other characters like the neighbors who interact with this 'angel' character, such as a curious child who looks up to the 'angel' or an elderly person who is helped by the 'angel' on a regular basis.