Well, it could be about their baby having some sort of special power. Maybe the baby inherits both rukia's shinigami powers and ichigo's hybrid powers. It could grow up in a world where it has to learn to control these powers while also facing the challenges of being the child of two very important and powerful beings.
The fanfiction could start with the baby girl already being a few years old. She has an in - built talent for seeing spirits like Ichigo. Rukia tries to teach her about the Soul Society while Ichigo wants her to have a normal life in Karakura Town. This creates a conflict between them, and the baby girl has to navigate between her parents' different desires while also dealing with her own emerging powers.
Well, one possible plot could be that Ichigo and Rukia have to protect their baby from some new and powerful enemy in the Soul Society. Their baby might inherit some unique powers from both of them, and they have to train the baby while also keeping it safe.
The plot might involve Aizen being released from his imprisonment somehow and seeing the new - born as a threat. Since Ichigo and Rukia are powerful in their own right, their child could potentially grow up to be even more powerful. Aizen could try to manipulate the situation to either turn the baby to his side or eliminate it. But Ichigo and Rukia's love for their child would be a strong force against Aizen's evil intentions.
One possible plot could be that Ichigo kidnaps Rukia out of a desperate need to protect her from some unseen and extremely dangerous threat in the Soul Society. He might believe that the Soul Society's own mechanisms for safeguarding her are insufficient.
One possible plot could be that rukia and byakuya accidentally end up taking care of a baby. They initially struggle as they are not used to this situation. Byakuya with his strict nature tries to impose order while rukia is more lenient. As they care for the baby together, they start to understand each other on a deeper level and their relationship grows stronger.
It could be some rogue shinigamis who oppose the idea of rukia and ichigo having a child together. They might see the baby as a threat to the existing power structure in the Soul Society.
The new addition to their family could also make them more open about their feelings for each other. They might realize how much they truly care for one another while watching their baby grow. This could lead to more affectionate moments between them and a more solid romantic relationship.
One possible plot could be that Ichigo and Rukia are paired for a school project. They start off not getting along very well because of their different personalities. Ichigo is impulsive and Rukia is more reserved. But as they work together, they gradually learn to understand and respect each other. They might face challenges like finding a suitable topic, dealing with difficult classmates who try to disrupt their work, and finally presenting their project successfully which also strengthens their friendship.
It could be about a moment of unexpected closeness between Ichigo and Rukia in a closet. Maybe they are hiding from some danger or just stumbled into this confined space, and this leads to some deep conversations and a new understanding of their relationship.
Ichigo might become more reliant on Rukia's knowledge of the Soul Society when it comes to teaching their daughter about her heritage. Rukia, in turn, would rely on Ichigo's human - side experiences to give their daughter a well - rounded life. Their relationship would evolve into a partnership in parenting, with mutual respect growing even more.