In the 'ichigo is grimmjow's pet fanfiction', it could start with Grimmjow capturing Ichigo during one of their intense battles. Grimmjow sees Ichigo as a unique find and decides to keep him around instead of killing him. He puts Ichigo in a situation where Ichigo has limited freedom and has to rely on Grimmjow for basic necessities. As time passes, Ichigo tries to break free from this pet - like status, but also starts to understand Grimmjow's past and the reasons behind his aggressive behavior. This new understanding might lead to a change in their relationship, from a captor - pet dynamic to something more complex and perhaps even an alliance against common enemies.
Well, one possibility could be that Grimmjow has some personal vendetta against Ichigo. Maybe he wants to use Ichigo as a bargaining chip with the Soul Society. He could be tired of Ichigo always getting in his way during battles and decides to take him to a secluded location where he can deal with him on his own terms.
The main antagonists could be other powerful Hollows who don't like Grimmjow having a human - like Ichigo as a pet. They might see it as a sign of weakness or an abnormal behavior and try to attack Grimmjow to get rid of Ichigo.
In the fanfiction, perhaps they are forced to team up due to a common enemy. As they spend time together, they realize they have more in common than they thought. Female Ichigo might be intrigued by Grimmjow's wild nature, and Grimmjow could be attracted to her strength. They could end up having deep conversations about their pasts and their places in the world, and this could lead to a strong emotional bond between them.
Well, one possible plot could be a story full of chaos. Maybe it's set in an alternate universe where the normal rules of the 'Bleach' world are bent. Grimmjow, being pregnant, might struggle with his own identity and the changes in his body. Gin could be either supportive or have some ulterior motives. It could explore how the other characters react to this unexpected situation, like some being shocked and others trying to use it to their advantage.
One idea could be that they are rivals in high school sports, like on the track team. Grimmjow is overly competitive and Ichigo is determined not to let him win all the time. Their rivalry gradually turns into an understanding and then friendship, and maybe more as they discover they have more in common than they thought.
Rukia would be extremely worried. She would likely try to gather her friends in the Soul Society and form a rescue party. She has a strong bond with Ichigo and would not stand by while he is in danger. She might also be a bit angry at herself for not being able to protect Ichigo in the first place.
Some possible titles could be 'Female Ichigo's Encounter with Grimmjow', 'The Bond Between Female Ichigo and Grimmjow', 'Female Ichigo and Grimmjow: An Unlikely Pair'.
One possible plot could be that Naruto, after being exposed to some strange chakra or magic, starts to take on Grimmjow's aggressive and fearless attitude. He might become more impulsive in battle, like Grimmjow, and start to challenge his enemies without much thought for strategy at first. His friends would be confused by this sudden change in his behavior.
Common themes include the struggle for identity. Ichigo is part - Hollow and Grimmjow is an Arrancar, and they both have identity issues to some extent. Fanfics often deal with how they come to terms with who they are. Another theme is the idea of second chances. Given their initial enmity, fanfics might give them a second chance at a relationship, whether it's a friendship or something more complex. And of course, the theme of power - sharing and cooperation, as they learn to use their powers together in some fanfics.
One popular story could be 'Ichigo's Unexpected Bond with Grimmjow'. In this fic, their relationship develops in a unique way, perhaps starting from a fierce rivalry and gradually turning into something more. It might explore how Ichigo's understanding of Grimmjow deepens over time.