Maybe in the fanfiction, baby Naruto has a nightmare. Kushina then holds him close, reassuring him that he's safe. She could tell him stories about his father, Minato, and how they both love him very much. This would comfort Naruto and he'd soon fall back asleep in her warm embrace.
In this fanfiction, it could be that Kushina and Naruto are having a lazy day. As Naruto starts to feel sleepy, Kushina takes him to their cozy little corner. She lays down with him and Naruto snuggles up to her. Kushina strokes his hair gently until he falls asleep, all the while thinking about how precious he is to her.
Kushina would take care of baby Naruto very tenderly. She would make sure he is well - fed before sleep, perhaps by breastfeeding him or giving him a warm bottle. She'd also check his diaper and change it if needed.
One possible development for Naruto is that he begins to show signs of leadership. Even as a baby, he might gather the other village kids around him and lead them in some small play - adventures. For Kushina, she could develop a more nurturing side. She might start to think more about the well - being of the whole village because she realizes that Naruto will grow up in this environment. So, she could be involved in activities that improve the living conditions in the village, all because of her love for Naruto.
One possible reason could be mind control. Maybe an enemy of the village found a way to manipulate Kushina's mind and make her turn against her own baby. Another reason might be a misunderstanding. For example, she could have been tricked into believing that Naruto was a threat to the village in some way.
In this type of fanfiction, it could be that Kushina has a misunderstanding about Naruto's goals. For example, if Naruto starts to befriend some people from other villages that are seen as potential enemies by Konoha. Kushina, being a very loyal Konoha - nin, disowns him. Naruto would have to prove that his actions are for the greater good of all villages and not just Konoha.
One possible plot could be that Kushina, using her unique abilities or knowledge, helps Naruto gain an edge in his training. Maybe she imparts some secret jutsu or gives him advice on how to better control his chakra, which he then uses to overcome a powerful enemy.
One possible plot could be an alternate universe where time and events are distorted. Maybe some time - travel or magic is involved that leads to Naruto being in a situation where he could get Kushina pregnant. It would be a very strange and complex plot, considering Kushina is Naruto's mother in the original story.
One possible reason could be for Naruto's protection. Maybe she thought by banishing him from a certain place or situation, she could keep him away from a hidden danger that she knew about. For example, there might be a powerful enemy targeting Naruto specifically, and she believed that by making him leave, he would be harder to find.
One possible reason could be some sort of dark influence or curse that makes her lose her maternal instincts. Maybe a powerful enemy targets her and in order to protect Naruto from further danger related to her, she feels forced to abandon him. Another reason might be that she is made to believe false information about Naruto, such as that he will bring great disaster to the village in the future.
One possible reason could be a mission. In many Naruto - related stories, missions often take characters away from their families. Naruto might have received a highly important and dangerous mission that requires him to be away from Kushina for a long time.
Maybe she's been possessed. In some fanfictions, characters can be taken over by dark forces. So Kushina could be under the control of some evil entity and that's why she hurts Naruto.