Harry Potter himself could be a potential Avatar of Death. Given his connection to Voldemort and all the death and sacrifice he has witnessed, he might develop some sort of connection to death in a more profound way. It would be a very dark and different take on his character, but it could also add a whole new layer of depth.
They are popular because Aang is such a beloved character. His death in a fanfic creates a lot of drama and allows for exploration of different characters' emotions. Fans like to see how the other characters would react and grow in the face of such a great loss.
It could be an ancient dark ninja who wants to use Naruto's new 'avatar of death' powers for his own evil purposes. This ninja might have been researching death - related jutsus for years and sees Naruto as the key to his ultimate power.
One possible 'Avatar Aang death fanfic' could be about how his friends deal with the grief. For example, Katara might struggle with the loss of her love while also having to step up and be a stronger leader in the Water Tribe. Another could focus on how the world changes without Aang's presence to maintain balance. Maybe new benders emerge in unexpected ways to fill the void he left.
One idea could be Naruto having an encounter with a death - like entity that grants him new and dark powers. He might struggle with the morality of using these powers while still trying to protect his village.
Another aspect could be the character development. If a character becomes an Avatar of Death, it would change their personality and motives completely. They might start seeing life and death in a very different way, perhaps even challenging the moral and ethical boundaries that are so important in the Harry Potter series. For instance, they could question the value of sacrificing oneself for the greater good when they have a new perspective on death.
Often, it might be that Harry has a series of encounters or quests that lead him to connect deeply with the concept of death and thus evolve into the avatar. This could involve facing deathly challenges, understanding the afterlife, or mastering forbidden spells related to death.
I recommend the following novels with the male protagonist traversing the world of Death: Naruto: The Strongest Yin Escape, Rebirth in the 2D World, Death's Doujinshi, Machete Cold, Death's Fanatic, Crying Villain, Death's Temptation, Death's Forced Business, Online Games 'Death to Invincibility, Death's Fanatic, Death's Temptation, etc. These novels covered the plot of the male protagonist transmigrating to the world of Death, and some of them also included harem and longer elements. I hope you like these recommendations!
Grace is presumably the protagonist. Since the story is named 'grace and the time machine story', she is the central figure. She may be an ordinary person at first, but through her association with the time machine, she embarks on extraordinary journeys through time. Maybe she's a curious person, always eager to explore and learn, which is why she gets involved with the time machine in the first place.
Natalia Grace is the person at the heart of this complex story. She was adopted, and then there were doubts and disputes regarding her age and behavior within her adoptive family.