Perhaps a mysterious figure who has been observing Sakura from the shadows. This person, for some reason, decides to train her to be an assassin. He could have some ulterior motives, like using Sakura for a grander plan, but still teaches her valuable skills along the way.
One key plot point could be Sakura's training. She might start from being a novice, learning various assassin skills like stealth, combat, and weapon handling. Another point could be her first mission. It could be a dangerous one where she has to prove herself. Also, her relationships with other characters in the assassin world, whether they are mentors, rivals or allies, would be important in shaping the story.
In this fanfiction, Percy could be an assassin who is on a quest to find a powerful artifact. This artifact was stolen by a rival group and is being used for evil purposes. He travels across different lands, using his assassin skills to gather information, fight off enemies, and finally retrieve the artifact to save the world.
One idea could be that Altair, after being hurt as a kid, is taken in by an assassin. He trains hard to overcome his pain and fear, gradually becoming a skilled assassin. He might have a mentor who helps him channel his anger into his training and missions.
Sakura's teammates Naruto and Sasuke could be her allies. Naruto might support her with his charisma and influence among the villagers, while Sasuke could offer his combat expertise and strategic knowledge.
Well, one interesting aspect could be the character development of Sakura as an assassin. Maybe she has to overcome her own moral boundaries to carry out her missions. Another aspect could be the action scenes. How she uses her assassin skills to fight opponents would be exciting to read about.
Well, perhaps Percy starts off as an ordinary character but gets drawn into the chaos realm. He could be forced to become an assassin due to some threat to his friends or family. Maybe he discovers new powers that make him suitable for this role.
Rock Lee could be a great ally for Sakura in this fanfiction. His unwavering determination and loyalty would be assets. He could help Sakura train physically and also be a source of moral support. Also, Tsunade, Sakura's mentor, would surely play a role. Tsunade could offer her wisdom and guidance, especially in matters related to leading the village, as she was once a Hokage herself.
Her friends Naruto and Sasuke could be her main supporters. Naruto, as the Hokage or a very influential figure in the village, could publicly endorse Sakura's bid for kage. He might see in her the qualities that are necessary for leadership. Sasuke, with his power and unique perspective, could also support her privately by providing advice on security and dealing with external threats. Their combined influence would give Sakura a significant boost in her journey to become kage.