They could study ancient scrolls. In the Naruto world, there are often hidden scrolls with powerful jutsu. A character might stumble upon one that has the secrets of a new space - time jutsu. By deciphering the symbols and practicing the techniques described, they could develop the new jutsu.
One idea could be a story where Naruto discovers a new, ancient space - time jutsu that allows him to travel to alternate universes. In these universes, he meets different versions of his friends and enemies, and has to find a way to return home while also dealing with the chaos caused by the jutsu's power.
A 'Solar - Flare Rasengan'. Naruto could combine his wind - style chakra with some kind of solar - based energy he discovers. This jutsu would be like a super - charged Rasengan that emits a blinding light as well as powerful wind - based damage.
There could be a jutsu that allows for instant teleportation across long distances. This jutsu might be a new discovery in the fanfiction world, perhaps created by a character who has been experimenting with space - time ninjutsu. They might use it to quickly get in and out of battles or reach far - off places in a blink.
It could be a new form of Rasengan. Maybe Naruto discovers a way to combine different elements with the Rasengan more effectively, like adding lightning to it for a more powerful and faster attack.
There's also the 'Inferno Storm Jutsu' in some fanfictions. It creates a large - scale storm made entirely of fire. The fire in this storm has different intensities, with the center being the hottest and most destructive. It can cover a large area, making it a great offensive move against groups of enemies.
Maybe Sasuke. Although they are rivals, they also have a deep bond. Sasuke might have come across a unique jutsu during his travels and decide to teach it to Naruto so that they can both become stronger and better protect their village.
It could be Naruto himself who discovers and uses the Katon Hijingakure no Jutsu in the fanfiction. Since he's always exploring new jutsus and pushing his limits.
He might learn a time - traveling jutsu. This would be really cool as it could allow him to go back and change certain events in the Naruto world, or gain knowledge from the past to use in the present battles.
Here are some recommendations for novels about space and time:
1. 'Celestial Master of the Mystic Way' and 'Soul Devouring Chaos' were both novels related to time and space. The main character of Heavenly Venerate Xuan Dao could control time and had an ancient divine artifact. He began his journey to dominate the world. The protagonist of " Chaos Devouring Soul " had a connection with time and space due to the arrangement of fate.
2. " The Legend of Time and Space Adventures ": The protagonist of this novel is a space traveler and a time traveler. He searches for the truth, walks in different heavens, and becomes a preacher and adventurer.
3. " The Time Plunderer: The protagonist of this novel is reborn as the Nightmare Elf Tokizaki Kozo. He has the ability to time and space in the Marvel World and becomes the only master.
Please note that the above recommendations are based on the search results provided. There may be other novels related to space and time.