The Akatsuki members could be the antagonists. Since Sasori was part of the Akatsuki, other members might want the scrolls for their own evil plans. They could try to stop Naruto from getting to the scrolls.
Maybe there's a new group of villains introduced specifically for this fanfiction. They could be a group of power - hungry ninja who heard rumors about Sasori's scrolls and are determined to get them at all costs. They set up various obstacles and battles for Naruto and his friends during their search for the scrolls.
There could also be some rogue ninja clans. They might see the power that Sasori's scrolls could hold, like advanced puppet - making or some forbidden jutsu. So they become the antagonists, trying to steal the scrolls from Naruto or whoever is in possession of them.
One possible plot development could be that Naruto discovers the scrolls in an old, abandoned hideout. Maybe the hideout is full of traps set by Sasori long ago. Naruto, with his ninja skills, has to overcome these traps to reach the scrolls.
One possible antagonist could be Vlad Masters. He might want to keep Danny's body for his own evil purposes, like using it to gain more power or to take over Danny's life. Another could be a powerful and vengeful ghost who has a grudge against Danny and sees his body as a way to get back at him.
The Akatsuki could still be the main antagonists. Even though Sasori is training Naruto, the rest of the Akatsuki might view Naruto as a threat and try to eliminate him. Also, Orochimaru could be an antagonist. He might be interested in the new skills Naruto is learning from Sasori and try to steal them for his own experiments.
He might discover a new type of chakra control method. His mother could have been an expert in chakra manipulation, and the scrolls could hold the key to a more advanced or unique way of using chakra, which would be a great asset for Naruto.
He could face booby - traps. Sasori was a master of puppetry and defense, so he might have set up various traps to protect his workshop.
In the fanfiction, the scrolls could reveal a lot. For example, they might disclose the circumstances of Naruto's birth. Maybe there are prophecies written in them about Naruto's future. There could be stories of his parents' love and how they made sacrifices for the village and for Naruto. It could also be that the scrolls contain some sort of training method that was unique to his family, which would help Naruto become even stronger as a ninja.
Danzo could be a main antagonist. He's always been power - hungry and has seen Naruto as a threat to his control over the village. After Pain's attack, he seizes the opportunity to turn the villagers against Naruto.
Perhaps an old enemy of the Fire Daimyo, like a corrupt noble or a power - hungry general within the Fire Country who sees Naruto as a threat to their plans of overthrowing the Daimyo. So they try to eliminate Naruto, but the Fire Daimyo intervenes to save him.
A new group of rogue ninjas could be antagonists. They might see Naruto's state of not caring as an opportunity to use him for their own evil plans. Maybe they try to manipulate him into helping them steal some powerful ninja artifacts or secrets, and when Naruto realizes their true intentions, he has to fight back.
Zeus could be one. He's the king of the gods and has a lot of power. His authoritative and sometimes unpredictable nature might put him at odds with Naruto.