He could do something really selfless to make it up to her. Maybe he takes on a dangerous mission that will benefit the village in a big way, and he does it in the name of making Kushina proud again. Or he could use his skills to help those in need in the village, like building homes for the poor or teaching the younger ninjas, which would show Kushina that he has grown into a responsible person.
Naruto could start by sincerely apologizing to Kushina. He needs to admit his mistakes and show that he truly understands how much he has hurt her. For example, if he made her cry because of his bad behavior, he should promise to change and actually follow through on that promise.
Build their relationship gradually. Start with small interactions like Naruto helping Kushina find something she lost. Then, as they spend more time together, they start to trust each other more. Slowly introduce deeper conversations about their fears and hopes. This way, the relationship feels natural and believable.
In some fanfictions, Kushina was sealed into Naruto through a complex jutsu. It might be a modified version of the sealing jutsu used to seal the Nine - Tails. The process could involve special incantations and chakra manipulations.
One great Naruto Kushina Devil May Cry fanfiction could be about Kushina having some sort of connection to the Devil May Cry world. Maybe she has a hidden power that is similar to the devil arms in Devil May Cry. For example, her chakra chains could be related to a special weapon in the Devil May Cry universe.
It could be developed through a series of events where Kushina tries to make amends. She might leave little signs or messages for Naruto, showing her love and regret. As Naruto starts to notice these things, he becomes curious about her true intentions. Eventually, they have a face - to - face encounter where Kushina explains everything. Naruto, seeing her sincerity and the love she has for him, forgives her, and they start to build a new, stronger relationship based on honesty and understanding.
Another aspect could be that the fanfiction delves into how Kushina's presence affects Naruto's relationships with others. For instance, his relationship with Sasuke could be different. With a strong maternal figure in his life, Naruto might be more stable emotionally and be able to approach Sasuke in a more understanding way, which could potentially change the whole dynamic of their rivalry and friendship.
Perhaps Kushina made a choice that Naruto felt was unfair to him. Like if she gave away something that was rightfully his, it could make him angry.
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.
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.
Their relationship could be developed through shared experiences. For instance, they could go on a mission together where they face a powerful enemy. During this mission, they would have to rely on each other's skills, which would deepen their bond.
It could be that Sakura betrays Naruto's trust. For example, if Naruto entrusts Sakura with a very important secret, like something related to his family or his new power he's developing, and Sakura reveals it to their enemies or uses it against Naruto in some way, that would be a huge blow to Naruto and could lead to him crying.