A good way is to put them in a situation where they have to rely on each other's strengths. Kushina's speed and chakra control combined with Issei's unique powers can create a synergy. As they see how well they work together, it can lead to a deeper connection, like a mutual admiration that blossoms into a strong friendship or more.
Another method is to introduce a conflict that only they can solve together. Maybe there's a powerful enemy that can only be defeated by combining Kushina's ninjutsu and Issei's special abilities. Overcoming this conflict would not only strengthen their bond but also give them a chance to learn more about each other on a personal level.
Their relationship could start with Kushina being curious about Demon Naruto's powers. This curiosity could lead to them spending more time together and gradually building trust.
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.
To develop their relationship realistically, start with them as friends. Have them share common interests like training or exploring the supernatural world. Then gradually introduce moments of deeper connection, like when one saves the other from danger.
A unique way to develop their relationship could be through a series of challenges. For example, they are trapped in a mysterious dimension together and have to rely on each other to escape. In the process, they discover each other's strengths and weaknesses, and Kurama realizes that Kushina is not just Naruto's mother but a powerful ninja in her own right. This mutual respect and reliance would strengthen their relationship.
In this type of fanfiction, their relationship could be developed through Naruto finding a way to communicate with Kushina's spirit. Through this communication, Kushina can share her experiences of being neglected with Naruto. Naruto, in turn, can tell her about his own struggles. This exchange of experiences can create a stronger bond between them, and Naruto can then strive to make sure that no one else in the village feels the neglect that they did.
In fanfiction, the relationship might start with curiosity. Kushina could be curious about Naruto's demon side. She starts to study it and in the process, gets closer to Naruto. As she helps him understand and control his powers better, they become friends. Then, as they spend more time together, they realize they have feelings for each other that go beyond friendship. They support each other through difficult times, like when Naruto has to face the negative aspects of his demonic form, and Kushina has problems in the village. This continuous support deepens their relationship.
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.
Their relationship could be developed uniquely by having them swap bodies for a while. This would force them to see things from each other's perspective. Issei would understand the pressures Rias faces as a devil princess, and Rias would get a taste of Issei's more carefree but determined human side.
Issei could develop by learning the discipline and self - control that comes with being an exorcist. This would contrast with his more impulsive devil - side nature. For example, he might have to resist the urge to use brute force and instead use the more strategic and spiritual techniques of an exorcist.
They can be developed as comrades in arms. They could be part of a female - only ninja squad where they learn to trust and rely on each other in battle. For instance, they might cover for each other's weaknesses during a difficult mission.