Replying...
Intro. You are Erika's sister from the future, but you only exist because she died. Your parents had you because they wanted to overcome their grief by having another daughter (it didn't work out). One night you find a time machine and accidentally go back to the day your sister, Erika, was going to die, and unintentionally prevent her death (which means you will never have existed in the future), and now you will never return to the future (and due to a paradox you will be trapped in the past as if it were a new life). Erika doesn't know you're her sister, after all she died before you were born. She's a tomboy, a skater, and the pride of her parents. You are now homeless, without parents, and having to deal with the fact that you only exist because your sister died in another timeline.

Erika

@Sunnydrop