Their comrades in the Soul Society might be initially shocked. Some might be very supportive, like Renji. He has a close relationship with both of them and would likely offer practical help. Others, who are more traditional, might be a bit distant at first, not knowing how to react to this unorthodox situation for Soul Reapers.
With the other captains, there could be a mix of reactions. Some may see it as a sign of a new era in the Soul Society and be positive. For example, Shunsui might find it interesting and offer his unique brand of support. However, there could be more conservative captains who worry about how it will impact the order and discipline of the Soul Reapers. And then there are the lower - ranked Soul Reapers who would probably look up to Rukia and Byakuya even more, seeing them as more relatable now that they are starting a family.
Regarding their enemies, it could change the dynamic completely. Enemies might see this as a weakness to exploit. They could target Rukia and Byakuya more, thinking that they are more vulnerable during the pregnancy. But at the same time, this could also inspire some of their former enemies to have a change of heart. Maybe they would respect the fact that they are about to be parents and leave them alone. It really depends on the nature of the enemies in the fanfiction world.
Rukia's kind and empathetic nature would make her very nurturing towards the baby. She would be quick to comfort the baby when it cries and would be very hands - on in its care. Byakuya, on the other hand, with his reserved and disciplined personality, might seem a bit cold at first. But his sense of duty would ensure that he provides for the baby's needs in a very organized and efficient way.
One great fanfiction could be one where Byakuya and Rukia have to team up for a special mission in the Soul Society. In this story, their relationship, which has always been complex, could be explored more deeply as they face various challenges together. It might show Byakuya's protective side towards Rukia that he usually keeps hidden.
With Rachel, Phoebe's pregnancy could make Rachel more aware of her own life choices. Maybe Rachel, who has had her own share of relationship and career ups and downs, starts to envy Phoebe's new - found family - building journey. Phoebe, on the other hand, might try to encourage Rachel to find stability. With Monica, Monica would probably be super organized about Phoebe's pregnancy. She'd be making meal plans and trying to get Phoebe to follow a strict schedule for the baby's health, which Phoebe might resist at first.
Orihime would probably be over - the - moon excited. She's always been a kind - hearted and emotional person. She would immediately start knitting baby clothes or making cute little charms for the baby. Chad would be very supportive as well. He would offer his strength to protect Rukia during her pregnancy. Uryu might be a bit more reserved at first, but deep down he would be happy for them. He might use his Quincy skills to create some sort of protective item for the baby.
Byakuya's personality is one of dignity and reserve. This affects his love for Rukia in that he doesn't easily let his feelings show. He is a man of few words, and when it comes to his feelings for Rukia, he is no different. But his love is manifested in his protectiveness. His noble upbringing means he has a code of honor, and part of that honor is now to protect Rukia. His love is a quiet, unassuming one that grows as he starts to understand Rukia more and more as a person, not just as a member of his squad.
Another theme is redemption. For example, if there was a situation where Byakuya made a mistake regarding Rukia in the past, a fanfiction could be centered around his journey to make it up to her. This could involve him facing his own pride and learning to be more open with his feelings towards her.
A pregnancy would likely strengthen their relationship. They would become more reliant on each other, sharing the joys and fears of impending parenthood.
It would likely change their relationship with their parents. Their parents might become more protective or concerned. For example, they could start giving more advice on how to raise a child. With their friends, some might be excited and offer to help, while others could be jealous or feel left out.
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.
One of the best aspects is their growth. In many fanfictions, we see Rukia growing from a somewhat naive Shinigami to a more powerful and confident one, and Byakuya's role in that growth, either as a guiding figure or someone she has to overcome. For example, he might teach her new combat techniques subtly.