He could practice in secret locations where no one can see him. For example, in an abandoned cave or a hidden part of the forest. That way, no one will know about the new jutsu he's developing.
Naruto could also pretend to be injured or exhausted after a fight and say that he can't use certain jutsu. But in reality, he's just saving those jutsu for a more important situation. He might even fake a chakra exhaustion so that his enemies and allies alike think he's out of powerful moves for the time being.
Perhaps Naruto hides his jutsu because he's being spied on by an unknown enemy within the village. He doesn't want to expose his new and powerful techniques until he can figure out who the spy is. So he acts like he's still relying on his old moves during training and small skirmishes.
Maybe he found some hidden scrolls left by his mother. These scrolls could have contained the details of her jutsu. Naruto, being the curious and determined ninja he is, would have studied these scrolls carefully and learned the jutsu.
In fanfic, Naruto may create his own jutsu based on his emotions. His strong will and never - give - up attitude can be translated into chakra - based techniques. For instance, when he's feeling extremely protective of someone, he channels that emotion into his chakra and creates a defensive jutsu. He also might draw inspiration from his memories. Remembering his training sessions with Jiraiya, he could take some of the basic techniques he learned and add his own twist to them, like adding a wind - element boost to a simple physical attack jutsu.
Well, it could be the Uzumaki Chain jutsu. In the Naruto lore, the Uzumaki clan had some unique abilities and the chain jutsu was one of them. His mother Kushina was from the Uzumaki clan, so it's possible that's the jutsu he learned in the fanfiction.
If Naruto creates a very powerful and dangerous jutsu, some characters might be afraid of him. For example, the villagers who were once suspicious of his Nine - Tails power could again start to fear him. However, his close friends like Sasuke and Sakura would likely trust him and help him control and master the new jutsu.
Well, in many such fanfictions, Naruto might start learning his father's jutsu when he discovers some hidden scrolls or when a mentor who knew his father decides to teach him. Maybe it could be someone like Jiraiya who reveals some secrets about his father's techniques.
Another reason could be related to his personal growth. He might be trying to master the power of the eye in private. Naruto has always been one to face challenges alone at first. By hiding his eye, he can focus on understanding and using its power without distractions or the pressure of others' expectations.
Well, he might use simple distractions. For example, he could create a minor commotion to draw attention away when he's about to use a particular skill subtly. Maybe he pretends to be clumsy or make a small mistake on purpose so that others don't suspect he has advanced skills.
With his friends like Sasuke, Naruto's new ability might cause some jealousy at first. Sasuke is always striving to be stronger, and seeing Naruto master such a powerful jutsu could make him feel a bit left behind. But in the long run, it could also motivate Sasuke to improve himself further and their rivalry could become even more intense.
To create a jutsu in Naruto Jutsu Maker Fanfic, look at the existing jutsus for inspiration. Notice how they are named, what they do, and how they are used in battles. You could base your new jutsu on a character's personality or backstory. If your character has a connection to water, like growing up near a big lake, maybe the jutsu involves creating huge water serpents. Another aspect is the chakra consumption. Decide how much chakra your jutsu will use. If it's a very powerful jutsu, it should probably consume a lot of chakra, but you can also create some low - chakra - cost jutsus for quick and repeated use.