In a 'Naruto raised by Shinigami' fanfiction, the story could go in many directions. The Shinigami might train Naruto in secret, away from the prying eyes of the Hidden Leaf. Naruto could be taught how to use reaper - like powers, like being able to sever spiritual bonds. This would give him an edge in battles against enemies who rely on normal ninjutsu. Also, his relationship with the Nine - Tails might be affected as the Shinigami has its own connection to powerful entities.
The plot could be really interesting. Naruto, being raised by the Shinigami, would likely have a very different upbringing compared to the original story. He may not have the same level of loneliness as he was constantly in the presence of the Shinigami. The Shinigami could have passed on some of its knowledge about the balance of life and death. This could lead to Naruto having a more nuanced view on protecting life. He might also develop a unique fighting style that combines Shinigami - related abilities with his own ninja skills. For example, he could use his shadow clones in a way that mimics the Shinigami's multiple arms or something similar.
In this fanfiction, the story might start with Naruto being found or taken in by the Shinigami. The Shinigami could train Naruto in a different way than the regular ninja training. Naruto could learn secrets about the afterlife which could give him an edge in battles. He may also have a strange connection with the souls, which could be both a strength and a burden. For example, he might be able to communicate with the souls of fallen ninjas and gain their knowledge or power.
The plot might revolve around Harry having to keep his relationship with the shinigami a secret from the wizarding world. As he grows up, he starts to notice how his upbringing by a shinigami gives him an edge in dealing with dark magic. He could use the knowledge of the shinigami to face Voldemort in a way that no one else could, like understanding the true nature of death and using it to his advantage.
Naruto would probably be more independent in his thinking. Instead of relying on the typical ninja values taught in the village, he'd draw from the Shinigami's teachings. This could make him a bit of a rebel in the eyes of the ninja community. He might question the established norms more often. His development would also be influenced by any special tasks or missions the Shinigami gives him. For instance, if he has to deal with restless souls, it would make him more empathetic towards those in pain, but also more determined to maintain the order between the living and the dead.
The plot might involve Naruto being sent to the Shinigami realm for some reason. There, he has to adapt to the rules and powers of the Shinigami. He could make allies among the Shinigami and bring back some of their knowledge and powers to his own world, causing a stir among the ninja clans. He might also face challenges from Shinigami who don't trust him at first because he's an outsider.
Well, in this 'naruto champion of the shinigami fanfiction', it could be that Naruto is chosen by the Shinigami for a special mission. The Shinigami might see something unique in Naruto, like his strong will or his ability to never give up. So, Naruto is made the champion. As the champion, he could be tasked with maintaining the balance between the living and the dead in the Naruto world. This would likely involve battles against those who try to disrupt this balance, such as evil spirits or necromancers. He may also have to face his own inner demons and learn how to control the power of the Shinigami without being consumed by it.
I'm not sure specifically as there could be many different plots in such a fanfiction. Generally, it might involve the Naruto character who is a Jinchuuriki (a host of a tailed beast) having some sort of connection or interaction with the Shinigami (the god of death in some contexts). It could be about how his Jinchuuriki powers are affected by this connection, or perhaps adventures that come from it.
He'd probably be more solemn. The Shinigami is a being associated with death, so Naruto would be exposed to serious concepts early on.
Well, it could involve a character making a deal with a Shinigami. Maybe a ninja is on the verge of death and in order to gain some extraordinary power to save their village or loved ones, they make this contract. The Shinigami might demand something in return like a part of their soul or their future memories.
I'm not entirely sure as it depends on the specific fanfiction. But generally, it might involve Naruto having some sort of divine or shinigami - related origin, which could lead to him having special powers or a different path in his ninja journey.
Maybe the Shinigami uses its special powers to heal Naruto's severe injuries. For example, it could transfer some of its own spiritual energy to Naruto to revive his fading life force.