Yes, Age regression is stated in the title. If it was a regression of mind then fair enough, if it was even the body diminishing to that of a younger person; but for a nineteen year old to try pretend to be ten (or younger) whilst still having the face and physique of a nineteen year old, I maintain, is 'Far Fetched'
My problem with this one is that there... doesn't really seem like any good reason for anyone to mistake the 19 year old boy for a 6 year old girl. It defies belief that anyone could make that mistake. This is a problem that could easily be solved by same random magical explanation... like a curse that makes other people think that he's a little girl and treat him accordingly. Without that kind of an explanation, everyone's acceptance of the disguise is completely unbelievable. It's like if a little kid drew a police badge in crayon and pinned it to his shirt, and everyone believed that he was a police officer as a result. Sure, you can tell a story like that; it's just not a reasonable story.