Well, Naruto could bring his unique sense of justice to Fairy Tail. Since he has always been about protecting his friends and village, he would likely jump into any situation in Fairy Tail where the guild or its members are in danger. His Rasengan could be a very powerful attack against the various foes in the Fairy Tail world. And he could learn some magic from the Fairy Tail wizards too, like how to control magical elements which would be a whole new experience for him.
They could go on a quest to find a lost magical crystal. Naruto's tracking skills as a ninja and Sayla's knowledge of the Fairy Tail world's magic locations would be useful. Along the way, they might encounter various magical creatures and have to fight them using Naruto's jutsu and Sayla's magic.
The guild master could embark on a quest to find ancient and powerful magic artifacts. For example, they might search for a lost crystal that has the power to enhance the magic of all guild members. This would involve traveling to dangerous and mysterious places, like a forgotten underground temple filled with traps.
The Fairy Tail guild would probably be very curious about Naruto at first. They might be amazed by his strange abilities like running up walls and creating clones. Some members, like Lucy, would likely be a bit cautious, but also intrigued. Natsu would probably be eager to test his strength against Naruto right away.
Perhaps they go on an adventure to find a healer who can ensure a healthy pregnancy. Along the way, they face various challenges like traversing through dangerous terrains. Jellal uses his magic to protect Erza and the unborn child, while Erza uses her combat skills when necessary. This adventure could also strengthen their bond with their guildmates as they all work together towards this important goal.
Imagine an adventure where they are sent to the past. They have to ensure that an important event in Fairy Tail's history happens correctly. Lucy and Loki have to blend in with the past guild members without changing too much. This involves Loki having to hide his modern magic tricks and Lucy having to be careful with summoning her celestial spirits so as not to arouse suspicion.
She could have adventures where she uses her Pokemon to explore new areas in the Fairy Tail world that are too dangerous for normal mages to go alone.
He would have his Rinnegan as well. With the Rinnegan, he could potentially control the six paths of magic in the Fairy Tail universe. For instance, he could use the Deva Path to manipulate gravity - something not common in the Fairy Tail magic system. His Preta Path could absorb magical attacks, making him a formidable opponent against even the most powerful Fairy Tail mages. His other paths like the Asura Path could give him additional mechanical - like appendages with enhanced strength and weaponry, which would be a new and terrifying concept in the Fairy Tail world.
One possible storyline could be Naruto joining Fairy Tail and having to prove himself to the guild. He'd use his wind mage powers to take on quests and fight against dark guilds. Another could be him facing off against a powerful wind - based enemy in the Fairy Tail world and having to learn new techniques to defeat them.
He could have an interesting relationship with Natsu. Natsu is known for his hot - headedness and love for a good fight. The Hulk, with his anger - based power, could be a great sparring partner for Natsu. They might start off as rivals, constantly trying to outdo each other in terms of strength. Or they could become friends who understand each other's need to let out their pent - up energy. He could also have a relationship with Lucy. Lucy might be a bit intimidated by him at first, but as she gets to know him, she could see his good side and try to help him control his anger. Maybe she could use her celestial spirits to calm him down in some situations.
He could go on rescue missions. For example, if a villager is in trouble in a far - off place, Naruto could quickly drive his car there. His car might be modified with some ninja - like features, like a hidden compartment for his shurikens and kunais.