Perhaps in this one - shot, there is a magical spell that temporarily brings Kushina's spirit back to the world of the living. Naruto meets her and they have a long conversation. Kushina shares her experiences and wisdom with Naruto, and Naruto tells her about all the things he has accomplished and how he has made their family proud. This encounter gives Naruto a new sense of purpose and connection to his family heritage.
One possible plot could be a heart - warming mother - son moment where Kushina imparts some important life lessons to Naruto. For example, she could tell him about the Uzumaki clan's history and how to better control his chakra. Another idea might be a story set in a parallel universe where Naruto and Kushina have an adventure together, perhaps facing a new and unknown enemy. They could use their combined skills and the unique Uzumaki abilities to overcome the challenges.
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.
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.
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.
It could also be due to some external influence. Perhaps an enemy used some kind of mind - control or manipulation on Kushina. They made her think that Naruto was a threat, so she decided to disown him. In the Naruto universe, there are many powerful villains who could potentially do this kind of thing.