The Soul Reapers could be involved too. Some of them might notice that Ichigo is acting strange and try to figure out what's going on. Captains like Byakuya or Kenpachi could potentially cross paths with Ichigo during this time. And then there are the Hollows. They might sense that something is different about Ichigo but not be able to fully understand why he seems weaker than before, which could lead to some interesting confrontations.
In some fanfictions, there could be new characters introduced specifically for this arc of Ichigo getting his powers back. For example, an old and powerful soul reaper who has some special knowledge or ability related to Ichigo's powers. They could play a crucial role in guiding Ichigo, training him, or even sacrificing themselves to help him regain his powers. Additionally, villains would also be main characters in a sense. They could be the ones who initially took Ichigo's powers or are trying to prevent him from getting them back, thus creating the conflict in the story.
Perhaps in the fanfiction, Ichigo hides his powers because he wants to live a normal life for a while. He could be tired of all the battles and responsibilities that come with his power. So, he tries to blend in at school and with his family, but of course, it's not easy as his true nature keeps showing up in small ways.
Rukia could also be in the fanfiction. Given their close relationship, she might be the first one to notice something is off with Ichigo. She could be the one trying to keep him out of trouble or scolding him for getting drunk in the first place.
The main character is Merlin, of course. He is the focus as he is the one with the hidden pain. Arthur Pendragon is a key figure too. Since Merlin is Arthur's manservant, Arthur's actions, words, or even his ignorance of Merlin's true self can be sources of Merlin's pain. Sometimes, the Great Dragon can also be involved. The dragon might be aware of Merlin's pain and offer some cryptic advice that Merlin has to decipher while still hiding his pain from others.
Naruto is the central figure in this 'naruto imprisoned by his family fanfiction'. His family, including Minato and Kushina, are likely to be directly involved in his imprisonment. However, other characters from the Naruto universe might also play a role. For instance, Jiraiya could be a character who tries to find out why Naruto has been imprisoned and works towards his release. Also, Sasuke might get wind of Naruto's situation and decide to take action, either to help or because he sees it as an opportunity to gain an advantage.
Well, obviously Ichigo himself is the central character. His friends like Orihime and Chad may also play important roles. They could be there to support Ichigo as he discovers more about his heritage. And of course, Rukia is likely to be involved. Since she was the one who initially introduced Ichigo to the world of Soul Reapers, she might have some insights or be part of the story as Ichigo uncovers the secrets of his heritage.
Obviously Naruto himself is the central character since the story is about him losing his memories. Sakura would likely be involved too. She's one of Naruto's closest friends and a medic - ninja, so she might try to find a way to restore his memories.
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.
There could be new characters specific to the village where he becomes Kamikage. For example, some powerful shinobi clans within that village. Their leaders would be important as they could be Naruto's allies or opponents. Also, the previous Kamikage's advisors might still be around and play a role in guiding or challenging Naruto. Maybe an old sage - like figure who has deep knowledge of the village's secrets and helps Naruto understand and respect the village's heritage.
Batman's allies such as Commissioner Gordon could be involved. Sometimes Batman might be angry at Gordon if he feels that the police force is not doing enough to support his fight against crime. Also, other members of the Bat - family like Batgirl could be part of the story. Their actions or decisions might trigger Batman's anger. For instance, if Batgirl decides to take on a powerful villain alone against Batman's advice.