It could be Jiraiya. Jiraiya was Naruto's mentor and taught him a lot of important skills. He might have come across this unique needle - shooting technique during his travels and passed it on to Naruto. Jiraiya had a vast knowledge of different jutsu and combat techniques, so it's not far - fetched that he could have introduced Naruto to this.
Maybe Kakashi. Kakashi is known for his innovative combat techniques. He has seen Naruto grow and develop over time. He might have noticed Naruto's potential with needles (maybe Naruto was already good at using needles in some basic way) and taught him how to shoot them like arrows as an advanced form of the technique.
It could be related to a hidden bloodline limit. Although Naruto doesn't have a traditional bloodline limit like the Uchiha's Sharingan, perhaps there is some long - lost aspect of his Uzumaki heritage that enables him to shoot needles like arrows. This could have been dormant until he reached a certain level of power or had a specific encounter. For example, it might be connected to the Uzumaki's strong life force and ability to manipulate energy in unique ways.
An older, more experienced ninja from a hidden village that specializes in needle - based jutsu could become his mentor. This ninja could have unique insights into the art of using needles, teaching Naruto different formations and strategies for using them in battle.
You can try fanfiction websites like FanFiction.net or Archive of Our Own. They have a large collection of fanfictions from various authors. Just search for 'Arrow Naruto' on their search bars, and you'll be presented with a list of relevant stories.
His father, Minato, could be a likely candidate in a really dark fanfiction. Maybe he was resurrected in an imperfect way and his mind was warped, causing him to turn on Naruto.
A prevalent theme is the exploration of different cultures. The feudal Japanese - inspired world of Naruto and the more contemporary, Western - style world of Arrow offer a great contrast. Fanfictions might explore how the characters from each world react to the cultural differences, and how they might learn from one another. It can be a really fascinating exploration of two distinct fictional universes.
Jiraiya could be one to support Naruto. Jiraiya has a connection with Naruto already, and he's the type who goes against the norm. He would likely take Naruto under his wing and help him grow in strength and confidence away from Konoha.
His mother, Kushina, could also be part of the family that wants him back. She was a kind - hearted and strong - willed woman. If she were alive in the fanfiction, she would be desperate to have her son with her. She would want to protect Naruto and share all the things she didn't get to when he was growing up, like teaching him about their Uzumaki heritage.
Obviously Naruto is one of the main characters since it's in the title. There might also be his friends like Sasuke or Sakura. They could be either helping Naruto in his skewer - arrow adventure or be in need of his help.
His friends like Sakura, who is a medic - ninja, would surely be the first ones to try to help. She could use her medical knowledge and skills to diagnose Naruto's illness.
His mentor, Kakashi, would also be there to help. Kakashi is very protective of Naruto. He would use his experience and calm demeanor to make sure Naruto gets the best possible care and support during this crisis.