Here's a random idea and starter for a realistic fiction short story. Based off of my own life but changed a bit.

There is a disorder in which a part of your brain does not allow you to recognize faces.
Prosopagnosia. Face blindness.
You cannot possibly imagine what it's like. The feeling of not recognizing anyone in a crowd is your daily struggle. You don't recognize your mom, your siblings, your friends, by sight. Their voices and clothes are all you can recognize. Everything else is strangely familiar.
The worst part is that you look in the mirror and the person looking back at you is always a total stranger.

My name is Amelia. I'm sixteen.
I had to take notes on my appearance earlier.
My eyes are blue, my hair is a generic shade of brown and of average length. Somewhere between curly and straight. Lucky for me there's nothing particularly remarkable about my looks.
As a matter of fact, there is nothing remarkable about me in general, except for the prosopagnosia.
I have three best friends, Ashley, Amanda, and Chris, and an amazing boyfriend, Thomas. I don't think I could possibly have gotten this far in high school without their support.
It's my second-to-last year of public school. I want to tell the world how strange living with this disorder is.
The world will know.