My Childhood Buddy is a Girl?!

The idea I have here is two childhood friends.  YC has always been a tomboy. So there are no stereotypical girly hobbies/possessions. She has short hair, a gender neutral name (Like Chris or even Bobby). She dresses like a boy other than her underwear.  

So as kids, there was no way to know YC was a girl. She never said she was a girl. MC never saw her naked and she was often away with her family during the summer so MC never saw YC in a swimsuit. MC just always assumed she was a boy and YC never said otherwise. 

Of course this was a secret that time could not hide forever.  YC’s breasts have started to grow. Even at age 14 they are still small enough that she can hide them with effort. Her ass and hips are filling out as well, but again...that can be hid fairly well. Plus MC is fairly oblivious and never even considered YC is a girl. (Perhaps she is developing a crush and/or lust for him?)

I’d like a RP that starts out with their childhood days of just having fun and playing towards teenage years. Eventually I want MC to find out...not sure when or how that will happen, but it is going to happen!

Honestly once the secret is out...I am not certain if they both try to continue as things were, but it is more awkward with the truth out? Or if one or both of them know it will never be the same so they go towards romance/exploring their sexuality? Either way...before too long, they start talking about sex and agree to try and keep doing it after they start.

I would like to start this RP at age 9 or 10. I would then like to play some time lapses until they are 14-16 (when MC finds out). I expect YC to be similar in age (a year older or younger...)

Again the focus would be in exploring as they shift from pure friendship to a strange mix of friends, sex friends, and couple.  A relationship they try to keep the same, but they can't prevent the change, though the changes are fairly subtle and gradual to the point they might not even always be aware of them and whether or not the girl remains quite so tomboy, or decides to 'feminize' at least somewhat under the circumstances. (I’m certainly open to some changes if my partner has feedback...just let me know )

Thanks!