Okay so crackpot theory.
There is a connection between MC and Charlie; we can intuit this from a few deductions. One, they look similar. Two, Shopkeeper refers to them both as Charlie. Three, ???. Four, profit.
We know that Charlie is younger than the MC. Now I don't quite recall how old she is, but she kinda looks to be around the age range that MC was when his accident occurred. So bear with me, but what if Charlie was once a part of the MC?
We know that in order to give birth to the MC, Syla had to modify herself in some way such that she was capable of conception. Now since we know she was nearly purely Memory, that means that some other power was necessary in order for this to work. The most logical choice being Truth.
Now this would unfortunately mean that the MC would no longer be a perfect balance of Body and Memory. He would have some amount of Truth in him, but we have never even seen a hint of this. In fact, from all accounts, he seems to be purely Body and Memory. So then where did the Truth part of him go?
Charlie's power is based on Truth. She looks very similar to the MC, and she is roughly at an appropriate age range.
What I think happened is that Syla literally tore Charlie out of the MC to ensure that he was pure/balanced enough for the Third's plans.