It could be a young, inexperienced mage who has always admired Natsu from afar. Maybe someone with a hidden power that Natsu senses and decides to take under his wing.
Perhaps the apprentice could be a character who has lost their way in the world of magic. Natsu, seeing their potential, decides to be their mentor. This character might have some connection to Natsu's past, like being from the same village or having a relative who knew Natsu. So Natsu feels a sense of responsibility towards them.
The apprentice could be a completely new character created specifically for this fanfiction. This new character could have a unique personality, like being very shy but having a great deal of natural magic talent. Natsu would then have to break through the shyness to bring out the best in this apprentice.
Well, in this kind of fanfiction, Natsu might teach his apprentice about magic. He could pass on his unique fire - based magic skills, like how to control the intensity of the flames. And they might go on adventures together, facing various challenges and enemies. Maybe the apprentice has some special abilities that Natsu has to help develop.
Maybe Valerie could be the apprentice. She has her own experience with fighting ghosts, so she would already have some skills. But as an apprentice to Danny, she could learn new techniques and ways of dealing with ghosts. Also, the dynamic between her and Danny could be really interesting, as they've had their share of conflicts in the past. It would be cool to see them work together in a more positive way. And there's also the potential for her to learn about Danny's secret identity in a new and different way as his apprentice.
The apprentice could be a new genin who shows great potential in the field of intelligence gathering. Maybe someone with a sharp mind and an ability to stay calm under pressure, like Shikamaru. He has the intelligence and strategic thinking that would make him a good candidate for Ibiki's apprentice.
Perhaps Neville Longbottom could take on this role. He has shown great courage throughout the series. His experiences with loss, like the death of his parents, could lead him down a path where he becomes the apprentice of death, using his newfound powers to protect others and bring a new balance to the wizarding world.
One suitable character could be a healer's daughter. She has grown up seeing the power of natural remedies and has a natural inclination towards magic. She is kind - hearted and intelligent, which would make her a great apprentice for Merlin. Also, a young noble who has been shunned by his family for his strange dreams (which are actually premonitions due to his budding magic) could be an interesting choice. Merlin would see the potential in him and take him as an apprentice.
Maybe an orphan from a non - Uchiha clan who has a special ability that Madara finds interesting. This character would be malleable and eager to learn from Madara, as they have no other real family or guidance. They could bring a fresh perspective to Madara's teachings.
He could marry an original character created specifically for the fanfiction. This character could be a powerful mage from a far - off place who crosses paths with Natsu during one of his adventures.
It could be a jealous rival from another guild. They might see Natsu as a threat and figure framing him would be a good way to get him out of the way.
Lupin could be a very interesting mentor. He could teach an apprentice about dealing with their own inner demons, as he has his own struggles with being a werewolf. He could also pass on his knowledge of defensive magic and how to use magic in a more practical and street - smart way.
A human with a mysterious past, like a former street urchin from Coruscant who has a natural affinity for the Force. This character would start off very naive about the ways of the Sith but quickly learn under Vader's harsh training. Their journey from a nobody to a powerful apprentice could be full of twists and turns.