Often, there is a trope of the Kyuubi being possessive in a motherly sense. It doesn't like other people or things that might harm Naruto. So it would be very wary of any new threats or characters that come too close to Naruto. And sometimes, there's a trope of Naruto and the Kyuubi having a kind of mother - son telepathic connection, where they can communicate their feelings and thoughts without speaking.
A frequent trope is the emotional bond between them. Naruto might seek comfort from the Kyuubi during tough times, and the Kyuubi would be there for him. There could also be a trope where Naruto tries to make the Kyuubi proud, similar to a child trying to impress their mother. He would constantly strive to become stronger and better at using the Kyuubi's power in a positive way.
In such fanfictions, the relationship between Naruto and Kyuubi can be developed in various ways. For example, the Kyuubi could start teaching Naruto about his heritage in a more motherly way, like sharing stories of the Uzumaki clan. Naruto, on the other hand, could show his loyalty and love towards the Kyuubi as he would to a mother. This could also impact his relationships with other characters. His friends might be initially confused but later come to understand and support this new relationship of Naruto's.
One interesting 'Naruto Kyuubi Mother' fanfiction could be where the Kyuubi's mother has a backstory of being a powerful spirit from an ancient era. In the fanfic, she might be trying to protect Naruto from afar, using her hidden powers to influence his growth and development.
One common theme is family. Since Kushina is Naruto's mother, fanfictions often explore the family bonds. They might show how Naruto's connection to Kushina affects his relationship with the Kyuubi. Another theme is power. The Kyuubi's power within Naruto is a huge aspect. Fanfictions may deal with how Naruto learns to control it, and how Kushina's own experiences with the Kyuubi's power can help or hinder Naruto. Redemption can also be a theme. The Kyuubi, which was once seen as a monster, could be redeemed through its relationship with Naruto and the influence of Kushina's memory.
A frequent theme is the struggle between good and evil. Dark Naruto represents a darker side, and the Female Kyuubi can be seen as either a force for good or bad depending on how the story is written. Their relationship also often explores themes of trust and betrayal as they try to figure out if they can rely on each other.
One common theme is power growth. Naruto's development of new skills under the fem Kyuubi's training is often explored. Another is the relationship aspect, like whether they become friends or something more. And there's also the theme of self - discovery for Naruto as he learns more about himself through the training.
Some common themes are power and its control. Since Kyuubi is a very powerful entity, fanfictions might explore how Naruto learns to control the power she gives him in a more nuanced way. Family and acceptance is also a big theme. Naruto, who grew up without parents, now has this 'mother' in Kyuubi. Fanfictions could show how he comes to terms with this new form of family. Additionally, the protection theme is there. Kyuubi, as Naruto's 'mother', would naturally want to protect him, and this can lead to many interesting plotlines where she defends Naruto from various threats.
One popular trope could be the 'mentor from the beyond'. Where a dead person acts as a mentor to Sakura, guiding her in her ninja skills or in understanding her power better.
Well, a frequent theme is the struggle for acceptance. Naruto as a Hanyou might face discrimination in the Naruto world, and the fem Kyuubi, being different as well, could share that struggle. Also, adventure themes are common. They might go on quests together, fighting enemies and discovering new things about their powers and the world around them. And of course, there's the theme of identity. Both characters have to figure out who they are in this new context of Naruto being a Hanyou and the Kyuubi being female.
One common theme is power. Since Kyuubi is a powerful entity, fanfictions often explore how Naruto's relationship with Kyuubi affects his power growth. Another theme is friendship or a deeper bond. Given that Naruto has a unique connection with Kyuubi, stories might focus on how they come to understand and trust each other more over time.
In some fanfictions, Naruto's mother, Kushina, has a special connection with the Kyuubi. For example, some stories might explore how Kushina's chakra influenced the Kyuubi's behavior. Since she was the Jinchuriki before Naruto, her relationship with the Kyuubi could be a rich source of plot development in fanfiction.