It could be that Zetsu, seeing Naruto's potential, decides to train him in order to use Naruto for his own mysterious purposes. Zetsu might start by teaching Naruto how to better sense chakra, not just the amount but also the nature and origin of it. This would enhance Naruto's ability to detect enemies and allies alike. As Naruto progresses in this training, he might start to suspect Zetsu's true motives but continue regardless to become stronger for the sake of his village and friends.
Well, one possibility could be that Zetsu imparts some unique and dark jutsu to Naruto. Maybe Naruto starts to learn stealth and subterfuge skills from Zetsu, which are different from what he learned at the ninja academy. This could lead to Naruto having an edge in certain battles where traditional ninja skills aren't enough.
It's likely that Naruto's chakra control and power would develop in new and unexpected ways. Black Zetsu might introduce him to strange chakra - based abilities that are not part of the normal ninja training. This could give Naruto an edge in combat, but it also might make him a target. Since Black Zetsu has his own motives, Naruto could be dragged into some dangerous and complicated situations that he may not be fully prepared for.
In a fanfic where Naruto is trained by Zetsu, the story could take an interesting turn. Zetsu has knowledge of the Akatsuki and their secrets. Naruto could learn about the organization from the inside out. This knowledge could help him in his quest to bring peace. He might also gain some physical enhancements. Zetsu is quite durable in his own way, and Naruto could inherit some of that sturdiness. This would make him an even more formidable opponent in battles against strong foes like Pain or Madara.
There could be internal antagonists within Naruto's own village. Some of the more conservative ninja in the village might not trust Naruto's new - found skills and powers obtained from Zetsu. They could try to undermine Naruto or even attempt to exile him, fearing that he has been corrupted by Zetsu's teachings.
I'm not sure specifically as there could be many different interpretations in fanfiction. But it might involve Zetsu using his unique abilities to rescue Naruto from a dangerous situation, like a powerful enemy attack or a life - threatening trap.
Well, it could be about Naruto being forced into a dark situation where he has to train for killing. Maybe he's been misled or there's a great threat that makes him think this is the only way. For example, he might be tricked by an enemy who disguises as a friend and convinces him that the only way to protect the village is to become a killer.
Well, in such a fanfiction, Naruto might learn unique skills from the summons. For example, he could learn stealth from a cat - like summon or brute strength tactics from a bear - like one.
In the 'naruto trained seriously fanfiction', Naruto could be training with his friends in a more serious way. They might form a special training group where they push each other to their limits. For example, they could be training to improve their teamwork and combination jutsus. Naruto might focus on his speed and strength training while also learning how to better coordinate with his friends' abilities, like Sasuke's Sharingan - based attacks and Sakura's medical and combat skills.
In this fanfiction, perhaps Naruto could learn some unique jutsu from Asuma. Asuma was known for his wind - style jutsu, so he might teach Naruto advanced wind - style techniques that Naruto could incorporate into his Rasengan, creating a more powerful attack.
In the fanfiction, Naruto could also develop new strategies for fighting. Pein is a strategic mastermind, and under his training, Naruto might learn how to better analyze his opponents, anticipate their moves, and come up with more effective battle plans. This could give him an edge in future battles against powerful enemies.
In this fanfiction scenario, Kurenai could also help Naruto with his emotional control. Naruto has a strong will but sometimes his emotions can get the better of him. Kurenai, with her calm and collected nature, could teach Naruto how to stay focused and in control during intense situations. For example, she could use her own experiences to show Naruto how to channel his emotions into strength rather than letting them cloud his judgment. This would not only improve his combat abilities but also his decision - making skills.