Something I scratched together:
<div class='spoiler_toggle'>Spoiler: click to toggle</div><div class="spoiler" style="display:none;">Okay, this goes with the travelling from the future to the past.
Someone goes to the past, to destroy the Earth. No one knows why. You wake up one morning, without a memory, on top of a building. You look around, but see no one. A flying car rushes by... "Where... Where am I?" Suddenly, you hear footsteps, you look behind you, and coming at you on the roof, is a teen with a gun. He lunges towards you and knocks you off the 40 story building. Next thing you know, everything goes black. You wake up in someone's house. You try to get up, but the girl, around 17, your age, lies you back down. "I don't know how you survived, but you managed to come out of that, unhurt. It's been weird ever since the (insert villains' name here) took over. They've made all of the humans live down here, while all other creatures get high exaltation." (Insert backstory here.) "So, what's your name?" (Type in your name.) "Nice name, I'm Karson Fellwin. My parents were killed a couple of years back, so now I can only live here. What's your story?" "I... I don't know, I lost my memory..." You say. "That sucks... Well, any idea who tried to kill you?" You shake your head no. "Well then, we should find out. Shouldn't we?" She winks. "Woah... we? I don't want to get you mixed up in this... Whatever THIS is..." "Look, (insert name), I have nothing to lose. So it's not like you'll be putting me in any danger."
Later on. You find out that someone is trying to blow up the earth.
Then, you find out you were part of the group that was trying to complete this objective. Your partner Karson is astounded and leaves you for the time being.
You then encountered the one who "tried to kill you". He then explains that he was your renegade partner from the future. He was trying to save you from a trap that had been set for you. The reason you forgot your memory was because the people who are cooperating with the future villains (the ones trying to blow up earth) erased your memory so that you would forget the fact that you were turning against them. You then set out with your partner/friend (insert name) to find Karson.
That's all I have for now. </div>