From that standpoint, the interface between self and brain is something like a mechanism for the one directing the operation of the other. The self is the result of the brain, and the brain exists to manufacture self to operate it. That's good for fictional characters who exist outside time & space, but not for real people -- it's perpetual motion.
This self-makes-self defies the laws of thermodynamics, which is why I believe the self is essentially a byproduct of the brain's need to direct a complex organism, not its purpose. Only for fictional characters can the self be the purpose.
What's interesting about that is the role of writers and readers in the creation of fictional selves. Fictional characters do not have a physical existence, but they certainly do exist in some way once read -- how many millions of people know Harry Potter better than they know their own best friend? What the created person lacks in terms of existing in time/space is compensated for by the fact that we can sit inside their minds, hear their thoughts, experience the sensations they receive.
As minds, we exist through language. Think of that. Without words, how can you be 'you?' It is in the naming of things that they become what they are, including ourselves. So with fictional characters, who exist only in language, there is a weird loophole that allows them to exist in a parallel way that is scarcely less real than ourselves. Don't believe it? Look at God and Jesus Christ. What is the proof of them? The Word, so important to millions of people that is its always capitalized, like the book in which it is recorded, is the proof.
For that matter, pick up a history book. Is it true? No. It's just a story of what happened. Yet we call a well-researched history text 'fact,' because it is known that what is said in the book reflects things that did occur. The entire thing is a fabric of conventions and understandings, not evidence -- not witness.
When I was a beginner, I wrote characters because I needed somebody to do what the stories required. These days, I write in order to discover who these people are. If we are ourselves a byproduct of the operation of the brain, the mind a kind of program that runs the organic machine -- then the fictional character, fully realized, is merely a diversion of the mind into running a conjectural machine.
So a superbly crafted fictional character is differentiated from a 'real' person only by a single degree, in that sense.
* We receive input (experience), interpret it through what we know (memory), and then develop an idea of what to do next (action); what we do, and how we do it, more or less defines who we are. I could be chock full of shit, of course.