In certain fanfiction concepts, Naruto might make a deal with some sort of spiritual entity. He sacrifices something of his own, like a part of his power or his future, in order to bring Kushina and Minato back. Or he could have harnessed the power of the tailed beasts in a new and unique way. The tailed beasts are extremely powerful, and if he could combine their power with his own in a specific way, it might be enough to revive his parents.
In certain fanfic concepts, Naruto could have found a special relic or artifact. This relic might have the power to reverse death. Since Naruto is always on adventures and exploring different places, he might stumble upon such an item and use it to revive Kushina. It could also be related to the Uzumaki clan's secrets that he uncovers which enables him to bring his mother back.
It could change the power balance in the ninja world. Other villages might see Konoha as a much greater threat with Minato and Kushina back. On the other hand, it could also lead to more cooperation as they might be seen as a symbol of hope. Emotionally, for Naruto, he would be able to learn more about his family, his heritage, and maybe even get some long - awaited parental guidance which would further develop his character.
In some fanfictions, Naruto might use some super powerful jutsu he created or mastered. Maybe it's a new form of Sage Mode that can reverse time on a small scale. Another possibility is that he found some ancient forbidden technique hidden in the Uzumaki clan's secrets.
Perhaps Naruto finds a way to travel back in time and prevent Kushina's death in the first place. He could use his Sage Mode or some other special ability to manipulate time. And then, by changing the past, he effectively'revives' her in the present. In the Naruto universe, there are all kinds of crazy powers, so time - travel isn't completely out of the question.
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.
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.
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.
One big impact would be on Naruto himself. Having his mother back would give him the family love he always longed for. He would have someone to share his problems and joys with on a more personal level.
In a fanfiction, perhaps Minato and Kushina are resurrected during a powerful enemy attack on the village. Naruto is in the middle of the battle when he suddenly sees his parents. At first, he can't believe it. Kushina runs to hug him tightly, while Minato stands there with a proud look. They then join the fight together, using their combined skills to defeat the enemy and have a moment of family reunion.
One possible fanfiction could be about Minato and Kushina watching over Naruto from the afterlife as he grows into a great ninja. They could be his silent guardians, influencing his decisions in subtle ways.