Well, in some fanfictions, Minato might use his powerful jutsu to break through the barriers between the living and the dead and directly reach Naruto. He could also try to influence the people around Naruto to bring him closer to where Minato is, like using his spirit to communicate with Naruto's friends and convince them to help.
Maybe they enlist the help of other powerful ninjas. For instance, they could ask Tsunade for medical support in case Naruto is injured. They could also get intel from Shikamaru, who is known for his intelligence. By gathering a team of reliable and strong ninjas, they increase their chances of getting Naruto back successfully.
Kushina could also seek the help of other powerful shinobi. For instance, she might ask Minato for assistance. Since Minato was Naruto's father and also a very skilled ninja, together they could come up with a plan to reunite with Naruto. Maybe they would use some sort of space - time ninjutsu to get closer to him.
One reason could be that Minato has some unfinished business with Naruto. Maybe he wants to pass on some crucial ninja skills or knowledge that only he can teach. Another reason might be the strong father - son bond. Despite being separated for so long, Minato's love for Naruto is still very deep.
On a more personal level, they could face internal guilt. As Naruto grows up and achieves great things on his own despite their neglect, Minato and Kushina may realize what they've missed out on. This realization could cause them a great deal of internal turmoil and regret for not being there for their son when he needed them.
In many Naruto fanfictions where Naruto meets Kushina and Minato, it often creates a very emotional scenario. Naruto finally gets to meet his parents who he has only heard about. It could be a heart - warming reunion where they share stories, hugs, and Minato and Kushina get to see how far Naruto has come.
One possible plot could be that Minato and Kushina are somehow brought back to life in a spiritual or semi - physical form. They then embark on a journey through the ninja world to find Naruto. Along the way, they encounter various characters who either help or hinder them. Maybe they have to face some old enemies who are still lurking in the shadows and trying to stop them from reuniting with Naruto.
At first, Naruto and Kushina might start to distance themselves from Minato. They could avoid him and not talk to him as much. As time goes on, the hatred might grow deeper. Naruto could start to oppose Minato in public or in important village matters. Kushina might also try to influence others in the village against Minato.
Naruto's reaction could be complex. On one hand, he would be extremely excited. But on the other hand, he would be worried about the consequences. He has learned about the balance of the ninja world and might be afraid that bringing Kushina back could have negative impacts. However, his love for his mother would probably overpower those concerns in the end, and he would still strive to make her return a reality.
Some members of the ANBU themselves could be antagonists. They might think that Naruto belongs with them and that Kushina is interfering in their affairs. They could try to keep Naruto in the ANBU by any means necessary, including using force or setting up traps for Kushina when she tries to approach Naruto.