Maybe in the fanfiction, an ancient evil has been awakened and it's up to Naruto, Sasuke, Sakura and the Sannin to stop it. The Sannin start by teaching Naruto, Sasuke and Sakura some long - forgotten jutsus. Naruto learns a wind - based jutsu that can cut through anything, Sasuke a fire - based jutsu that can incinerate entire armies, and Sakura a medical jutsu that can bring people back from the brink of death. They then embark on a dangerous journey to find the source of the evil and defeat it.
One plot idea could be that the Sannin discover a prophecy that only Naruto, Sasuke, and Sakura can fulfill. So they take the three under their wings more intensively. Jiraiya focuses on Naruto's spiritual growth, Orochimaru on Sasuke's control over his dark powers, and Tsunade on Sakura's physical and mental strength. As they train, they also uncover secrets about the ninja world that could change everything.
Well, they could start by having a friendly competition among themselves to see who has improved the most. This could lead to them realizing their combined potential. Then, they get called upon to deal with a threat that the old Sannin once faced but in a new and more dangerous form. Naruto might use his positive energy to boost the morale of the people around them, Sasuke would analyze the enemy's weaknesses, and Sakura would be ready to heal any injuries.
How about a story where an unknown enemy creates clones of them? Naruto, Sasuke, and Sakura have to not only fight these clones but also figure out who the enemy is and why they are being targeted. Along the way, they might discover new powers within themselves and also learn more about their relationships with each other.
In a fanfiction, there could be a story where a mysterious enemy targets Sasuke, Naruto and Sakura specifically because of their unique bond. The three of them then have to go into hiding and figure out who the enemy is and what they want. Along the way, they rely on each other's strengths and grow even closer as friends.
One possible fanfiction could be about how Naruto, Sasuke, and Sakura are trained by the Sannin in unique ways. For example, Naruto could be trained by Jiraiya in a new and more intense form of Sage Mode training. Sasuke might learn some long - lost Uchiha techniques from Orochimaru that change his perspective on power. And Sakura could be taught medical ninjutsu by Tsunade that goes beyond what she already knows, leading to her being able to heal even the most fatal of wounds in the heat of battle.
A fanfiction where they all go on a mission together in a strange, uncharted land. Kakashi is the leader as usual. Sasuke could struggle with his inner demons during the mission, Naruto would be trying to keep everyone's spirits up, and Sakura would be using her medical skills to keep them all in top shape. There could be new enemies and challenges that they have to face together, forcing them to rely on each other more than ever.
One idea could be a story where Sasuke and Naruto have to team up again for a dangerous mission, and Hinata and Sakura also join in. During the mission, Hinata might use her Byakugan to detect hidden enemies, while Sakura uses her medical and combat skills to support the team. And Sasuke and Naruto could have some deep conversations about their past and future, like they did in the original series.
One idea could be a time - travel fanfiction. Naruto, Sasuke, Sakura, and Kakashi are sent back in time to their early days at the academy. They have the knowledge of their future selves and use it to change some of the events that led to hardships in their lives. For example, Sasuke could prevent the Uchiha massacre with their combined help.
Maybe a plot where Sasuke and Sakura go on a mission together, and Naruto's family has to step in to help when things go wrong. For example, Sasuke and Sakura are sent to investigate a strange occurrence on the outskirts of the village. But they get trapped, and Naruto's son, using his unique skills learned from his father, manages to find and rescue them, strengthening the ties between the families even more.
One plot idea could be Sai trying to understand the deep bond between Naruto, Sakura and Sasuke. He might initially struggle as he has his own unique upbringing. For example, he could be assigned a mission with the three of them and slowly learn about their history, like Naruto's determination to bring Sasuke back and Sakura's unrequited love for Sasuke in the beginning. This could lead to Sai having a new perspective on friendship and loyalty.
A great plot for 'naruto sannin era fanfiction' would be to show how the Sannin's different ideologies started to form. Orochimaru's thirst for power might have begun with a particular event or discovery during this era. Tsunade could be shown dealing with the loss of her loved ones and how that shaped her views on life and the ninja world. Jiraiya's idea of finding the 'Child of Prophecy' might have been seeded during his experiences in the Sannin era as well.