A plotline could be that Nejibana is a weapon that was once used by a powerful and evil being. Ichigo is chosen to take it and purify it. He has to face the dark energy within the weapon as well as external enemies who want to use the weapon for their own evil purposes. This would be a great opportunity for Ichigo to grow both in power and in his understanding of good and evil.
One possible plotline is that Ichigo discovers Nejibana in a hidden location. Maybe it's in an ancient temple in the Soul Society that has been long forgotten. He senses its power and decides to take it, not fully aware of what it can do. Then he has to figure out how to use it while being chased by those who don't want him to have such a powerful weapon.
Another plotline might be that Nejibana is a key to unlocking a great power or mystery in the Bleach world. Ichigo gets Nejibana by accident, and then realizes that he's now in the middle of a big conspiracy. He has to rely on his friends and his own instincts to figure out what to do with Nejibana and how to stop those who are trying to use it for their own gain. Along the way, he might learn more about his own powers and the true nature of the Bleach universe.
In this fanfiction, Ichigo getting Nejibana could change the entire dynamic of the Bleach universe. Nejibana might have a unique ability that no other weapon has. Ichigo would need to learn how to control it. This could involve some training with characters who are more familiar with such weapons. The story could also explore how his relationships with other characters change. His enemies might be more afraid of him, while his friends might look at him in a new light. There could be a lot of action scenes where Ichigo shows off the power of Nejibana, like when he's facing a horde of Hollows or a powerful Arrancar. And as he gets more used to the weapon, he could even discover new forms or techniques that are unique to Nejibana.
A common plotline could be that the pregnancy changes their characters. Ichigo might become more protective and responsible, while Rukia could be more nurturing. They may also have to deal with their own insecurities. Rukia might worry about being a good mother, considering her past and her nature as a Soul Reaper. And Ichigo could be concerned about providing for the family. The story could also explore how their powers and abilities are affected by the pregnancy, if at all.
One plotline could be that they are kidnapped by a common enemy who wants to use their powers for some evil purpose. Maybe this enemy plans to extract the Mew Aqua from Ichigo and use Kisshu's alien technology.
Another plotline could be that Ichigo is transformed into a different form due to the Mugetsu influence in the fairy tale world. He then has to learn to control this new form while also trying to break a curse that has been placed on the fairy tale world. This would involve him interacting with different fairy tale characters, some of whom might be initially distrustful of him, but as he proves himself, they become his allies.
Perhaps Ichigo discovers his time - control ability while in a desperate battle. He suddenly realizes he can slow down time around him, giving him an edge over his opponents. This could lead to a series of battles where he has to learn to control this new power precisely. He might accidentally send himself into the future at some point and see a desolate world. Then he has to figure out how to prevent that future from happening. Maybe he teams up with some of his friends who also have unique powers, and together they use his time - control ability to solve a mystery that has been plaguing the Soul Reaper world for ages.
A possible plotline could involve Fem Ichigo being a huge Harry Potter fan in her world, and she writes fanfiction about it. But then, magically, the characters from her fanfiction come to life in her world. Harry and his friends are confused about this new world, and Fem Ichigo has to help them adjust while also trying to figure out how this happened. They might also encounter villains from both universes who team up, forcing them to work together to defeat the combined threat.
One possible plotline could be that they go on a mission together and during the mission, they discover a new power within themselves. Another could be that they have a friendly rivalry which turns into a deeper understanding and friendship as they face various challenges in the Soul Society.
One possible plotline could be them dealing with the reactions of their friends and family. Their friends might be initially shocked but then offer support. Another could be their own personal growth as they prepare for parenthood, like Ichigo learning to be more patient and Rukia becoming more in tune with her emotions. Also, they could face challenges from the Soul Society if there are rules against such a union having a child.
Another plotline could revolve around them working together to save a comrade. They have to combine their skills, with Ichigo's brute strength and Unohona's healing abilities. Along the way, they start to understand each other's values better. Unohona might see Ichigo's unwavering determination in a new light, and Ichigo could respect Unohona's calm and collected nature even more. It's a story of friendship and cooperation.
One possible plotline could be a magical or supernatural occurrence that leads to the pregnancy in a non - sexual way. For example, a spell gone wrong or a unique power interaction.