Forgot the name of an anime I want to watch.

I was on Crunchyroll watching SAO, or Sword Art Online. Dring episode 16 in season 1, there was an add. I was like "I'm gonna watch that!" I remember it being called something like Kuna or something (I think) I remember the description, it was about how it was the girl's (I think her name was Kuna) 16th birthday and she lost everything. It was like "She became a girl...a woman...a warrior" I remember her having red hair. Please help <3