A young pair of friends (MxF) sexual experimentation

Finally making my post-platinum return to the bulletins.

The idea is a pair of young but long time friends, boy and girl.  Everything between them had been casual, it was very rare they had a reason to think about one being a boy and one being a girl.  But now, things are starting to change.  Purely out of curiosity, they decide to try having sex with each other.  A line is crossed.  Things change, but how remains to be seen.  The first few times are likely awkward but they want more.  They try different things.

Things change?  But how?  I'm pretty open on that.  Does sex just get mixed into their friendship?  Do feelings change?  Do one or both experiment with others?  Does the girl get pregnant?  Lighthearted/wholesome/serious/dark, it could go any number of ways.  Plenty of kinks both ordinary or niche could potentially be included.  It is rather basic idea that could go in any number of interesting ways.  I am looking to start shortly before the first time they do it, either one could potentially be the one to bring up the idea of trying sex.

The idea is probably a pretty strong mix of story and sex.