You remember being told about werewolves and how they come to be when the full moon is out. That is all that you know about werebeasts. Little did you know however that there are many different werebeasts, there could be werecats, weredogs, wereotters, werekangaroos, werecows, weremice, wererats, etc. And while many werebeasts come out when there is a full moon, what you don't know is if one is born during a Blue Moon, then they stay as a Werebeast forever, and never turn human again. They only keep their Human Mind and Intelligence, but they are a Werebeast in Body through and through.
You are one of those special cases. You were born as a Human Being boy and during a Blue Moon, when you came out of your Human Mother's womb and vagina, you were seen to have a Werebeast tail growing out of your human upper butt just above your human anus. There was some spell or blessing put on you to make you be a Human without a Werebeast tail and you also wouldn't be a Werebeast, but sadly this spell or Blessing will only protect you from turning into a Werebeast and growing a Werebeast tail until your 20th birthday. Even worse you will turn into a Naked Female Werebeast. You lived 19 happy years a normal Human Being boy, nothing seemed like it could go wrong. Life is so good so far.
Unfortunately now it is your 20th Birthday and it also happens to be a night with a Blue Moon, so your transformation into a Female Werebeast is going to be permanent. When you wake up you check yourself and notice that there are many things that are wrong.
First you see that your clothes are magically gone, as if they never existed, none are you in your closets nor on your body, so you are completely naked. You also see that your Penis and Scrotum and shrinking and disappearing until they become your Clitoris, Urethral Meatus, and Labia Majora, Minora, and Vagina. But this is only the Beginning, You feel like something is growing out of your spine and lower back and upper back just above your anus. OH NO! You are turning into a Naked Female Werebeast.