Maybe through a special ritual or spell. In the fanfiction, they might be forced to combine their powers to defeat an extremely powerful foe. The combination could result in a new form for Ichigo, where he has some of Halibel's physical features like her fins or her ability to control water on a large scale, while still maintaining his own Hollow and Soul Reaper powers.
Another way could be through a mutual understanding of their powers' essences. Since Ichigo has both Soul Reaper and Hollow powers, and Halibel has the power of a powerful Arrancar, they could find a way to synchronize the spiritual energy flows of their powers. This synchronization might allow Ichigo to access a new level of power where he can use Halibel's water - shaping abilities to create defensive barriers or offensive water constructs, all while using his own swordsmanship skills.
Their powers could be combined in a way where Ichigo's Zanpakuto spirit, Zangetsu, and Halibel's water - based powers merge. For example, Ichigo could gain the ability to use water - enhanced slashes that have the cutting power of his normal attacks along with the fluidity of Halibel's water attacks.
Perhaps a plot where Ichigo accidentally ends up in Hueco Mundo near Halibel's territory. She initially sees him as a threat but then discovers that he has no intention of harming her or her fracciones. This could lead to an exploration of their different worlds and cultures within the Bleach universe.
One plot idea could be that Ichigo and Halibel are forced to team up against a new, powerful enemy that threatens both their worlds. They start off distrusting each other but gradually learn to respect and rely on one another's strengths.
In a post - war scenario, their relationship could develop into a mutual respect kind of thing. They've both seen the horrors of war, and they understand each other's strength. They might start to meet occasionally to exchange stories and advice on how to keep their respective groups safe.
For Ichigo, he could develop a more nuanced view of the Arrancars. Through his interactions with Halibel, he might realize that not all Arrancars are pure evil. This could make him more open - minded in his future encounters with other Hollows. As for Halibel, she could start to see the value in the Shinigami way, especially Ichigo's sense of justice. It might make her question her own loyalties and purpose.
Another way Ichigo could get his powers back in fanfiction is through a magical or spiritual artifact. Maybe he discovers an ancient sword or a talisman that has the ability to restore his lost powers. This could be part of a grander plot where he has to go on a quest to find this item, facing various challenges and enemies along the way. During this journey, he might also learn more about the true nature of his powers and how they are connected to the overall 'Bleach' universe.
Maybe their powers could combine through a magical artifact. Say they find an ancient talisman that links their powers. When they touch it together, their powers merge, allowing Ichigo to use his Bankai with a Quincy - like energy enhancement, and Candice to have access to some of Ichigo's Hollow - based speed and agility. This could open up a whole new range of combat abilities for both of them.
Another theme could be the exploration of their different worlds. Ichigo is from the human world and Soul Society, while Halibel is from Hueco Mundo. Fanfictions might delve into how they bridge the gap between these two very different realms, perhaps through mutual understanding and cooperation. This can lead to interesting stories about cultural exchange in a sense, within the 'Bleach' universe.
To develop their relationship, start with small interactions. For example, the OC could save Halibel from a surprise attack by other Hollows. This would make Halibel curious about the OC. Then, have them exchange stories about their lives. Halibel could talk about her rise to become an Espada and the OC could share their origin story. Another way is to give them a common goal, like protecting a group of innocent Hollows from a cruel Arrancar. Working together towards this goal would bring them closer.
Yes, there could be many fanfictions exploring different relationships between Ichigo and Halibel. Some might focus on their friendship, or them as allies in battles. Fanfiction writers often come up with creative scenarios that don't involve the more extreme or inappropriate concepts like pregnancy.
Ichigo would develop a more patient side. Halibel's different way of thinking and her more reserved nature would force Ichigo to slow down and really think about his actions. He would also become more protective, not just of Halibel but also of the new relationship they are building. Halibel would start to open up more. She was always a bit of an enigma in the original story. But in this fanfiction, being married to Ichigo would make her more expressive. She would start to share her thoughts and feelings more freely, and her character would become more complex as she tries to balance her old self with the new self that is influenced by Ichigo and his world.