Orochimaru would be a great main antagonist. He's always been interested in power and the secrets of the body. Naruto's half - demon fox nature would be a prime target for his experiments. He could try to extract the power of the demon fox from Naruto, or use Naruto as a way to create his own brand of super - soldiers with demon - like powers.
One idea could be exploring how Naruto's half - demon fox nature affects his relationships differently. For example, some friends might be more fearful or in awe of his power. Another could be a story where Naruto has to go on a journey to fully understand and control his half - demon fox side without the help of his usual mentors, relying only on his own instincts and new, unexpected allies he meets along the way.
One possible plot could be Naruto discovers his half - angel, half - demon fox nature during a life - threatening battle. His angel side gives him the ability to heal and purify, while his demon fox side provides immense power. He struggles to balance these two sides as he faces powerful enemies who are either attracted to or threatened by his unique nature.
There are fanfictions where the half fox demon aspect of Naruto is explored in his relationships. Maybe he has a closer bond with a certain character because they understand his struggle with the fox demon inside him. For instance, Sakura could be more empathetic towards him and help him control his powers better in some fan stories.
Maybe a rogue ninja who has been experimenting with dark magic. He discovers Naruto's unique nature and wants to steal his power. He believes that by combining Naruto's angel and demon fox powers, he can become invincible. So, he sets out to hunt Naruto down and tries every trick in the book to get his hands on that power.
The allure of a fox demon Naruto fanfic lies in the combination of two different and exciting elements. Fox demons often have their own set of mystical abilities which can add a new layer of mystery to the Naruto universe. For instance, their ability to communicate with nature or their connection to ancient magic could create some really cool story arcs when combined with Naruto's ninja world.
One plot idea could be Naruto's struggle to balance the angelic and demonic natures within him. For example, the angelic side might push him towards peace and mercy, while the demonic side could fuel his power in battles but also lead to more aggressive tendencies. He could be constantly at war with himself, trying to decide which side to listen to in different situations.
It could be a time-travel fanfic where Naruto as a fox demon goes back or forward in time to face new challenges. Or it might be in a crossover with another anime where his fox demon nature plays a key role.
One common theme is the struggle for acceptance. Since the character is half - demon, they often face discrimination from both humans and demons in the Naruto universe. Another theme is the exploration of new powers. As a half - demon, the character usually has a unique set of abilities that they need to discover and master.
Well, Naruto would obviously be the main character as the story is centered around him being a half - demon. There might also be characters like Sasuke. Sasuke could be involved in Naruto's journey, perhaps initially being suspicious of Naruto's new powers but later coming to accept and even help him control them.