Definitely Tsunade. She has so much experience and knowledge in medical ninjutsu. Her backstory alone could be a great part of the fanfiction. Then there's Kabuto. Although he was on the wrong side for a while, his skills as a medical ninja are undeniable. He could be a complex character in the story, either reforming or causing more trouble. And don't forget about Ino. She has some medical knowledge too and could be part of a medical ninja team in the fanfiction.
Rock Lee could be an interesting character in this kind of fanfiction. He could use the Ninja Wire in his taijutsu - based combat, adding an extra element of surprise. Gaara might also be a good choice. He could use the wire in combination with his sand, perhaps using it to control the movement of his sand in more precise ways. Hinata could use the wire to enhance her gentle fist style, allowing her to strike from a greater distance while still maintaining the chakra - flow - based attacks.
Naruto himself is obviously a very popular character in 'naruto real ninja fanfiction'. Sasuke is also commonly featured as he has a complex relationship with Naruto. Sakura is another one, often involved in stories that explore her growth as a ninja and her relationships with the other characters.
One idea could be a story where a medical ninja discovers a new healing jutsu during a difficult mission and has to protect the knowledge from enemy ninjas. Another could be about a medical ninja who uses their skills to heal a long - forgotten and powerful ninja, who then becomes an ally. Or perhaps a story of a medical ninja training under Tsunade to become the best in the village.
Sasuke can also be a popular character in Naruto Ronin Ninja fanfiction. He might cross paths with Naruto during his ronin days, and their relationship could be explored in new and interesting ways. Maybe they have to team up again to face a common enemy, or they might be on opposite sides for a change.
Zabuza Momochi is quite popular. His unique sword - wielding skills and his complex relationship with Haku make him a great character for fanfiction. Writers often explore his backstory more deeply or create alternate scenarios where he survives and has further adventures.
Naruto himself is obviously a very popular character in this type of fanfiction, given that it's about a 'naruto cyborg ninja'. Sasuke could also be a popular character, perhaps as an adversary or an ally to the cyborg Naruto, depending on the plot.
Naruto himself is often a central and popular character in such fanfiction. His natural determination and growth as a ninja make him an ideal focus for stories about a prodigy.
Sasuke is often a popular character in Naruto black ninja fanfiction. His cool and brooding nature can easily be incorporated into the black ninja concept. He could be a black ninja with enhanced Sharingan abilities.
Naruto is obviously a very popular character in these fanfictions. His journey and character traits make him a great fit for stories involving devils and ninjas. Sasuke is also often included as his rival or sometimes as an ally in these unique scenarios.
Sasuke is often a popular character in such fanfiction. His brooding nature and his own journey as a sort of wandering ninja in the original series make him a great fit. Writers can explore more of his travels and the people he meets outside of the main Naruto storyline.