Regarding the fact that my best friend is a magical girl

On one hand, I save the world as a (super-powerful) magical girl; on the other hand, I must be wary of my best friend, who's a huge fan of magical girls. To prevent our friendship from turning sour, I swear I'll take this secret to my grave!
"If my identity is exposed, I'll graduate from my magical girl career!" Even though I made that vow, I never expected...