It's hard to say if it's common. There could be many people named 'bleach' out there, but we don't really know how many of them are fans of 'bleach' the series and also engage with fanfiction. It depends on how big the 'bleach' fan community is and how many people with that name happen to be part of it.
Mostly, it is legal to 'watch' (assuming it's in a form that can be watched like an audio - visual adaptation) Bleach fanfiction. Fanfiction exists in a legal gray area that is generally protected under the concept of fair use. This means that as long as the fan work is not competing with the official Bleach products in the market, and is more of a creative addition by fans for fans, it is legal. But of course, if the fanfiction starts to use copyrighted elements inappropriately or in a way that violates the original creator's rights, then it could cross into illegal territory.
Some characters might be shocked. For example, Ichigo might be surprised by the future battles and the development of his friends. He could see new powers emerging and might start to train harder in the present to face the future challenges.
In 'bleach watch future fanfiction', Ichigo and his friends from the original series like Uryu, Chad, and Orihime are likely to be main characters. Their combined efforts in facing new threats in the future are often a key part of the story. Also, some of the powerful captains from the Soul Society, such as Byakuya, might be important as they deal with the new situations in the future.
Well, Rukia is also quite popular in 'bleach watch death battle fanfiction'. Her unique powers and her relationship with Ichigo can add a lot of depth to the stories. And then there's Grimmjow. His wild and aggressive fighting style makes him a favorite for many fans when it comes to 'death battle' scenarios in the fanfiction.
It's not that strange when you think about it. Naruto is a curious character. He might be interested in different stories and universes. Just like how we like to explore different fictional worlds, he could be intrigued by the Bleach fanfiction to see new ideas and concepts that he might not have in his own ninja world.
Some characters might be amused. For example, Ichigo might find it interesting to see how fans imagine his adventures in different ways. He could chuckle at some of the more out - there scenarios.
Rukia would probably be very critical at first. Since she is quite serious, she might nitpick the inaccuracies in the fanfiction. But she might also secretly enjoy the ones that show her in a positive light, like those highlighting her friendship with Ichigo. In the Bleach universe, characters are used to their own stories, and fanfiction would be a whole new and unexpected take on their lives. The zanpakuto spirits might also have interesting reactions if they could read, as they have their own personalities and might be offended or flattered by how they are depicted in the fanfictions.
For the Soul Society, if the captains read fanfiction, it might disrupt their normal order. For instance, Byakuya might read a fanfiction that portrays his family in a different way. This could make him question some of his long - held beliefs about his clan. And if enough characters start believing in the fanfiction - inspired ideas, it could completely change the power dynamics and relationships in the Bleach world. The Quincy might also get involved if they notice the characters in Soul Society acting differently due to the influence of fanfiction.
It's not extremely common but it does happen. Some fans of anime in general are interested in exploring different fan - created stories across different popular series. Since both 'bleach' and 'naruto' are well - known shonen anime, there might be some overlap in the fanbases who like to check out what others have imagined in fanfiction.