Some characters might be shocked at first. For example, her close male friends might feel a bit betrayed or confused, especially if they had a certain type of relationship with her when they thought she was a boy. But then they could come to accept and support her.
The characters in DxD would be quite shocked at first. Ichigo's appearance and his powers are so different from what they are used to. For example, Rias Gremory would probably be intrigued by Ichigo. She might try to form an alliance with him, seeing his potential as a powerful ally. Issei, being the main character in DxD, would likely be both jealous and in awe of Ichigo's abilities, and might challenge him at first but then learn from him over time.
Well, there are also those characters who might be a bit shocked or confused. Take Levi from Attack on Titan. He's a very serious and no - nonsense type of character. If he were to read some of the fanfic about him that deviated too much from his own self - perception, like being made into a comical or overly emotional character in the fanfic, he might be taken aback at first. But then he might also realize it's just a different interpretation and not take it too seriously.
Korra would likely be very cautious at first. She's used to dealing with powerful opponents, but Hollow Ichigo's otherworldly nature would be something new. She might try to communicate with him, but if he showed aggression, she'd be ready to fight. Asami would probably be more strategic, trying to figure out his weaknesses. Mako and Bolin would be a bit more intimidated. Mako might use his lightning - bending as a first line of defense, while Bolin would be thinking of ways to use his earth - bending to either trap or slow down Hollow Ichigo.
Well, it depends on the nature of the fanfiction. Some anime characters might be amused if the fanfiction is light - hearted and full of comical situations. For example, if it's a fanfic about a cooking competition among the characters from a shonen anime, they might react with good - natured laughter and competitiveness. They could also be confused if the fanfiction takes their story in a very strange or unexpected direction, like suddenly making a character from a historical anime end up in a space adventure.
At the start, Ichigo would be defiant. He would not show any fear in front of Aizen. He might taunt Aizen, trying to get him to reveal his true intentions. As time goes on, he would start to feel a sense of isolation, but this would only strengthen his resolve. He would use his inner Hollow powers more freely, as he has no other option. He would also be constantly thinking about ways to turn the tables on Aizen and escape, and would be ready to take on any challenges that come his way during his captivity.
Rukia would probably be both amazed and a bit worried. Amazed at the new power Ichigo has, but worried about how it might change him. Chad would see it as a natural progression of Ichigo's power and be supportive. Orihime might be a bit scared at first, but then she would see the good in Ichigo's new form and try to encourage him.
Ichigo would likely be defiant. He's a fighter and would not easily submit to Aizen. He'd probably be constantly looking for a way to escape and would be sizing up Aizen's every move, trying to find a weakness.
Ichigo would also experience a period of sadness. He values his relationships, and when one is broken through betrayal, it would hurt him deeply. He might isolate himself for a while, brooding over what happened. But ultimately, he would use this experience to become stronger. He'd learn from it and be more cautious in future relationships, while still maintaining his core values of loyalty and trust.
Rukia would probably be very suspicious right away. She knows Ichigo well and would notice the strange changes in his behavior. She might try to confront him and figure out what's wrong.