One idea could be that Muramasa and Ichigo are forced to team up against a new and powerful enemy. They start off distrusting each other but as they fight side by side, they come to respect one another's skills.
Muramasa could develop a softer side. Usually seen as a rather cold and mysterious figure, through his interactions with Ichigo, who is full of passion and determination, he might start to show more emotions. He could become more empathetic towards others, especially those who are fighting for a just cause like Ichigo.
Maybe fem Ichigo has a different set of powers compared to Ichigo. In the fanfiction, they could train together to combine their powers in a unique way. For example, her powers might be more focused on defense while Ichigo's are on offense, and they learn to complement each other. This could lead to some interesting character development as they overcome their differences and work towards a common goal.
Maybe in the fanfiction, Ichigo gets lost in Hueco Mundo and Halibel finds him. Instead of attacking, she decides to help him find his way back. During their journey, they encounter various challenges and secrets about Hueco Mundo are revealed to Ichigo through Halibel. This could lead to a new understanding between the two species they represent.
Well, a possible plot could be that Bambietta loses her memory and Ichigo finds her. He decides to help her recover her memories while protecting her from those who would use her amnesia to their advantage. Or perhaps they meet in a parallel universe where the rules of their powers are different, and they have to figure out how to work together to get back to their own universes. Also, a story where they are both given a quest by a mysterious entity, and in the process, they learn more about each other's pasts and motives.
One plot idea could be Ichigo and Kukaku teaming up to fight a new and powerful Hollow. They could combine their unique abilities, like Ichigo's Zanpakuto skills and Kukaku's fire - based attacks. Another idea is a story where Ichigo has to protect Kukaku from an unknown threat within the Soul Society. Maybe there's a conspiracy and they have to uncover the truth together.
One interesting plot idea could be a story where Shirosaki and Ichigo are forced to team up against a new, powerful enemy that neither can defeat alone. This would require them to put aside their differences and learn to work together, leading to some tense and interesting character interactions.
One interesting plot idea could be Ichigo discovers a new power with Yoruichi's help. They go on a journey to master this power, facing various challenges along the way. For example, they might encounter powerful enemies who are also after this power.
One plot idea could be that Hollow Ichigo and Rukia are forced to team up against a new, powerful enemy that threatens both the Soul Society and the world of the Hollows. They start off distrusting each other but gradually learn to work together and understand each other's motives better.
One plot idea could be that Ichigo and Tia Harribel have to team up to face a new and powerful enemy that neither could defeat alone. They start off distrusting each other due to their different origins, but as they fight side by side, they gradually develop respect and a deeper connection.
A possible plot is that Squad 14 is accused of a crime they didn't commit. Ichigo, as the captain, has to prove their innocence. He'd have to search for evidence, face false witnesses, and battle against those who are determined to see Squad 14 disbanded. This would test his leadership and his loyalty to his squad.