Ichigo would probably be devastated. His trust in relationships would be severely shaken. He might become more withdrawn and focus even more on his battles and training, using it as an escape from the pain of the betrayal. He could also become more cynical about love and people in general.
Perhaps in the fanfic, Ichigo has changed a lot over time. He might have become too focused on his power and his battles. His partner could feel left out and alone. There could be someone else in their life who offers them the attention and affection they crave. In this case, they might cheat on Ichigo. Fanfic writers often like to take characters out of their comfort zones and explore how they react to difficult situations like this.
There's a fanfic called 'The Bond of Hearts'. It's set in an alternate universe where Ichigo and Orihime are childhood friends. It shows their relationship evolving over the years. It delves deep into their emotions and how they gradually realize their love for each other. The character development in this fanfic is quite engaging.
One aspect could be the psychological impact on Ichigo. If he's being brainwashed, he might lose his sense of self and his usual heroic nature. His relationships with his friends like Orihime, Chad, and Uryu could also be severely affected. For example, they might not recognize the brainwashed Ichigo and think he's turned against them. This could lead to some really intense and emotional scenes in the fanfic.
One great fanfic where Ichigo is injured is 'The Road to Recovery'. It shows how his friends and allies support him during his healing process. The author does an amazing job of portraying Ichigo's struggle with his injury, both physically and mentally.
One possible reason could be to gain more power. In the Bleach universe, the dead often possess unique powers or knowledge. By raising the dead, Ichigo might be seeking to learn from them or use their power to fight stronger enemies.
Uryu could be another supporter. Despite their differences in the past, Uryu has come to respect Ichigo. In this strange situation, he might use his intelligence to help Ichigo. For example, he could research any possible side - effects or solutions related to the mpreg. Orihime is also a strong candidate. She has feelings for Ichigo and would be very empathetic. She would likely offer her healing powers and motherly - like care to Ichigo during his pregnancy.
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.
One character that might betray Ichigo is Chad. In some fanfic scenarios, if Chad is corrupted by some dark force or if he discovers some 'truth' about Ichigo that he believes is a threat to the world, he could turn on him. Also, Orihime has the potential to be a betrayer in fanfictions. If she is brainwashed by an enemy, like a powerful Hollow or an evil Quincy, she could be made to act against Ichigo. Her powers are unique and if misused, could cause a lot of harm to Ichigo.
There are quite a few good ones out there. For example, 'Beyond the Final Form' is a fanfic that not only explores Ichigo's new powers but also the lore behind his final form. It has a complex plot that involves different Soul Society factions reacting to Ichigo's transformation. 'The Final Form's Purpose' is another one where the author tries to give a deeper meaning to Ichigo's final form, like it being a key to a greater mystery in the Bleach universe.